code cleanup: remove unused references to f_log

f_log is only used in compiledict.c.

src/libespeak-ng/synthesize.c

@@ -44,7 +44,6 @@
 #include "synthesize.h"
 #include "translate.h"
 
-extern FILE *f_log;
 static void SmoothSpect(void);
 
 // list of phonemes in a clause

src/libespeak-ng/wavegen.c

@@ -55,7 +55,6 @@ static void SetSynth(int length, int modn, frame_t *fr1, frame_t *fr2, voice_t *
 
 voice_t *wvoice = NULL;
 
-FILE *f_log = NULL;
 static int option_harmonic1 = 10;
 static int flutter_amp = 64;