Remove unused phoneme flags.

src/libespeak-ng/phoneme.h

 // phoneme properties
 //   bits 16-19 give place of articulation
 #define phARTICULATION 0xf0000
-#define phWAVE     0x01
 #define phUNSTRESSED 0x02
 #define phVOICELESS  0x08
 #define phVOICED   0x10
 #define phNOLINK   0x40
 #define phTRILL    0x80
 #define phPALATAL  0x200
-#define phSINGLE_INSTN  0x1000    // this phoneme has a single instruction program, with an implicit Return
 #define phBRKAFTER 0x4000  // [*] add a post-pause
 
 #define phNONSYLLABIC  0x100000   // don't count this vowel as a syllable when finding the stress position

src/libespeak-ng/synthdata.c

 			break;
 		}
 
-		if (ph->phflags & phSINGLE_INSTN)
-			end_flag = 1;  // this phoneme has a one-instruction program, with an implicit Return
-
 		if ((end_flag == 1) && (n_return > 0)) {
 			// return from called procedure or phoneme
 			end_flag = 0;