Rename src/libespeak-ng/{speak_lib => speech}.c.

Makefile.am

@@ -105,8 +105,8 @@ src_libespeak_ng_la_SOURCES = \
 	src/libespeak-ng/readclause.c \
 	src/libespeak-ng/phonemelist.c \
 	src/libespeak-ng/setlengths.c \
-	src/libespeak-ng/speak_lib.c \
 	src/libespeak-ng/spect.c \
+	src/libespeak-ng/speech.c \
 	src/libespeak-ng/synthdata.c \
 	src/libespeak-ng/synthesize.c \
 	src/libespeak-ng/synth_mbrola.c \