code cleanup: make LookupFlags() static

src/libespeak-ng/dictionary.c

 #include "synthesize.h"                    // for STRESS_IS_PRIMARY, phoneme...
 #include "translate.h"                     // for Translator, utf8_in, LANGU...
 
+static int LookupFlags(Translator *tr, const char *word, unsigned int **flags_out);
+
 typedef struct {
 	int points;
 	const char *phonemes;
 	return flags0;
 }
 
-int LookupFlags(Translator *tr, const char *word, unsigned int **flags_out)
+static int LookupFlags(Translator *tr, const char *word, unsigned int **flags_out)
 {
 	char buf[100];
 	static unsigned int flags[2];

src/libespeak-ng/dictionary.h

 int TransposeAlphabet(Translator *tr, char *text);
 int Lookup(Translator *tr, const char *word, char *ph_out);
 int LookupDictList(Translator *tr, char **wordptr, char *ph_out, unsigned int *flags, int end_flags, WORD_TAB *wtab);
-int LookupFlags(Translator *tr, const char *word, unsigned int **flags_out);
 int RemoveEnding(Translator *tr, char *word, int end_type, char *word_copy);
 
 #ifdef __cplusplus