phoneme_add_feature: support setting the voice features.

The 'fortis' feature is not used, so it has been removed.

src/libespeak-ng/compiledata.c

 	// flags
 	{ "wavef",        tPHONEME_FLAG, phWAVE },
 	{ "unstressed",   tPHONEME_FLAG, phUNSTRESSED },
-	{ "fortis",       tPHONEME_FLAG, phFORTIS },
 	{ "sibilant",     tPHONEME_FLAG, phSIBILANT }, // TODO (deprecated): use 'sib' instead
 	{ "nolink",       tPHONEME_FLAG, phNOLINK },
 	{ "trill",        tPHONEME_FLAG, phTRILL }, // TODO (deprecated): use 'trl' instead
 	{ "flag2", tPHONEME_FLAG, phFLAG2 },
 	{ "flag3", tPHONEME_FLAG, phFLAG3 },
 
-	// voiced / unvoiced
-	{ "vcd", tPHONEME_FLAG, phVOICED },
-	{ "vls", tPHONEME_FLAG, phFORTIS },
-
 	// vowel transition attributes
 	{ "len=",   tTRANSITION,  1 },
 	{ "rms=",   tTRANSITION,  2 },

src/libespeak-ng/phoneme.c

 	uvl = FEATURE('u', 'v', 'l'),
 	phr = FEATURE('p', 'h', 'r'),
 	glt = FEATURE('g', 'l', 't'),
+	// voice
+	vcd = FEATURE('v', 'c', 'd'),
+	vls = FEATURE('v', 'l', 's'),
 };
 
 uint32_t lookup_feature(const char *feature) {
 	case alp:
 		// FIXME: Not supported by eSpeak. Used in Chinese/Japanese ɕ and ʑ.
 		break;
+	// voice
+	case vcd:
+		phoneme->phflags |= phVOICED;
+		break;
+	case vls: // FIXME: This should be a phVOICELESS (!phVOICED) flag. Fortis/lenis are a different thing.
+		phoneme->phflags |= phFORTIS;
+		break;
 	// invalid phoneme feature
 	default:
 		return create_name_error_context(context, ENS_UNKNOWN_PHONEME_FEATURE, feature);