code cleanup: reduce global externs (#1536)

Contribute to #68

Reduce count of globals / externs that could be a file-local static
variables

src/libespeak-ng/dictionary.c

 	int ix;
 	unsigned int digit_count = 0;
 	char *p;
-	ALPHABET *alphabet;
+	const ALPHABET *alphabet;
 	int dict_flags0 = 0;
 	MatchRecord match1 = { 0 };
 	MatchRecord match2 = { 0 };

src/libespeak-ng/speech.c

 #include "voice.h"                // for FreeVoiceList, VoiceReset, current_...
 #include "wavegen.h"              // for WavegenFill, WavegenInit, WcmdqUsed
 
-unsigned char *outbuf = NULL;
-int outbuf_size = 0;
-unsigned char *out_start;
+static unsigned char *outbuf = NULL;
+static int outbuf_size = 0;
+static unsigned char *out_start;
 
 espeak_EVENT *event_list = NULL;
-int event_list_ix = 0;
-int n_event_list;
-long count_samples;
+static int event_list_ix = 0;
+static int n_event_list;
+static long count_samples;
 #ifdef HAVE_PCAUDIOLIB_AUDIO_H
-struct audio_object *my_audio = NULL;
+static struct audio_object *my_audio = NULL;
 #endif
 
 static unsigned int my_unique_identifier = 0;
 static int min_buffer_length = 60; // minimum buffer length in ms
 static espeak_ng_STATUS err = ENS_OK;
 
-t_espeak_callback *synth_callback = NULL;
+static t_espeak_callback *synth_callback = NULL;
 int (*uri_callback)(int, const char *, const char *) = NULL;
 int (*phoneme_callback)(const char *) = NULL;
 

src/libespeak-ng/synthdata.c

 int current_phoneme_table;
 PHONEME_TAB *phoneme_tab[N_PHONEME_TAB];
 
-unsigned short *phoneme_index = NULL;
-char *phondata_ptr = NULL;
+static unsigned short *phoneme_index = NULL;
+static char *phondata_ptr = NULL;
 unsigned char *wavefile_data = NULL;
 static unsigned char *phoneme_tab_data = NULL;
 
-int n_phoneme_tables;
+static int n_phoneme_tables;
 PHONEME_TAB_LIST phoneme_tab_list[N_PHONEME_TABS];
 int phoneme_tab_number = 0;
 

src/libespeak-ng/synthesize.h

 extern unsigned char *out_ptr;
 extern unsigned char *out_end;
 extern espeak_EVENT *event_list;
-extern t_espeak_callback *synth_callback;
 extern const int version_phdata;
 
 void DoEmbedded(int *embix, int sourceix);

src/libespeak-ng/tr_languages.c

 #define OFFSET_ETHIOPIC 0x1200
 
 // character ranges must be listed in ascending unicode order
-ALPHABET alphabets[] = {
+const ALPHABET alphabets[] = {
 	{ "_el",    OFFSET_GREEK,    0x380, 0x3ff,  L('e', 'l'), AL_DONT_NAME | AL_NOT_LETTERS | AL_WORDS },
 	{ "_cyr",   OFFSET_CYRILLIC, 0x400, 0x52f,  0, 0 },
 	{ "_hy",    OFFSET_ARMENIAN, 0x530, 0x58f,  L('h', 'y'), AL_WORDS },
 	{ NULL, 0, 0, 0, 0, 0 }
 };
 
-ALPHABET *AlphabetFromChar(int c)
+const ALPHABET *AlphabetFromChar(int c)
 {
 	// Find the alphabet from a character.
-	ALPHABET *alphabet = alphabets;
+	const ALPHABET *alphabet = alphabets;
 
 	while (alphabet->name != NULL) {
 		if (c <= alphabet->range_max) {

src/libespeak-ng/translate.c

 bool skipping_text; // waiting until word count, sentence count, or named marker is reached
 int end_character_position;
 int count_sentences;
-int count_words;
+static int count_words;
 int clause_start_char;
 int clause_start_word;
-bool new_sentence;
+static bool new_sentence;
 static int word_emphasis = 0; // set if emphasis level 3 or 4
 static int embedded_flag = 0; // there are embedded commands to be applied to the next phoneme, used in TranslateWord2()
 
 static int max_clause_pause = 0;
 static bool any_stressed_words;
 int pre_pause;
-ALPHABET *current_alphabet;
+static ALPHABET *current_alphabet;
 
 char word_phonemes[N_WORD_PHONEMES]; // a word translated into phoneme codes
 int n_ph_list2;

src/libespeak-ng/translate.h

 void InitNamedata(void);
 void InitText(int flags);
 void InitText2(void);
-ALPHABET *AlphabetFromChar(int c);
+const ALPHABET *AlphabetFromChar(int c);
 
 Translator *SelectTranslator(const char *name);
 int SetTranslator2(const char *name);

src/libespeak-ng/translateword.c

 static void ChangeWordStress(Translator *tr, char *word, int new_stress);
 static int CheckDottedAbbrev(char *word1);
 static int NonAsciiNumber(int letter);
-static char *SpeakIndividualLetters(Translator *tr, char *word, char *phonemes, int spell_word, ALPHABET *current_alphabet, char word_phonemes[]);
-static int TranslateLetter(Translator *tr, char *word, char *phonemes, int control, ALPHABET *current_alphabet);
+static char *SpeakIndividualLetters(Translator *tr, char *word, char *phonemes, int spell_word, const ALPHABET *current_alphabet, char word_phonemes[]);
+static int TranslateLetter(Translator *tr, char *word, char *phonemes, int control, const ALPHABET *current_alphabet);
 static int Unpronouncable(Translator *tr, char *word, int posn);
 static int Unpronouncable2(Translator *tr, char *word);
 
 	*word = 0;
 }
 
-static char *SpeakIndividualLetters(Translator *tr, char *word, char *phonemes, int spell_word, ALPHABET *current_alphabet, char word_phonemes[])
+static char *SpeakIndividualLetters(Translator *tr, char *word, char *phonemes, int spell_word, const ALPHABET *current_alphabet, char word_phonemes[])
 {
 	int posn = 0;
 	int capitals = 0;
 };
 
 
-static int TranslateLetter(Translator *tr, char *word, char *phonemes, int control, ALPHABET *current_alphabet)
+static int TranslateLetter(Translator *tr, char *word, char *phonemes, int control, const ALPHABET *current_alphabet)
 {
 	// get pronunciation for an isolated letter
 	// return number of bytes used by the letter
 	int n_bytes;
 	int letter;
 	int len;
-	ALPHABET *alphabet;
+	const ALPHABET *alphabet;
 	int al_offset;
 	int al_flags;
 	int number;
 	int vowel_posn = 9;
 	int index;
 	int count;
-	ALPHABET *alphabet;
+	const ALPHABET *alphabet;
 
 	utf8_in(&c, word);
 	if ((tr->letter_bits_offset > 0) && (c < 0x241)) {

src/libespeak-ng/wavegen.c

 
 static void SetSynth(int length, int modn, frame_t *fr1, frame_t *fr2, voice_t *v);
 
-voice_t *wvoice = NULL;
+static voice_t *wvoice = NULL;
 
 static int option_harmonic1 = 10;
 static int flutter_amp = 64;
 static int glottal_flag = 0;
 static int glottal_reduce = 0;
 
-WGEN_DATA wdata;
+static WGEN_DATA wdata;
 
 static int amp_ix;
 static int amp_inc;
 unsigned char *out_end;
 
 espeak_ng_OUTPUT_HOOKS* output_hooks = NULL;
-int const_f0 = 0;
+static int const_f0 = 0;
 
 // the queue of operations passed to wavegen from sythesize
 intptr_t wcmdq[N_WCMDQ][4];
 int embedded_default[N_EMBEDDED_VALUES]    = { 0,     50, espeakRATE_NORMAL, 100, 50,  0,  0, 0, espeakRATE_NORMAL, 0, 0, 0, 0, 0, 0 };
 static int embedded_max[N_EMBEDDED_VALUES] = { 0, 0x7fff, 750, 300, 99, 99, 99, 0, 750, 0, 0, 0, 0, 4, 0 };
 
-int current_source_index = 0;
-
 #if HAVE_SONIC_H
 static sonicStream sonicSpeedupStream = NULL;
 double sonicSpeed = 1.0;
 		case WCMD_MARKER:
 			marker_type = q[0] >> 8;
 			MarkerEvent(marker_type, q[1], q[2], q[3], out_ptr);
-			if (marker_type == 1) // word marker
-				current_source_index = q[1] & 0xffffff;
 			break;
 		case WCMD_AMPLITUDE:
 			SetAmplitude(length, (unsigned char *)q[2], q[3]);