Use constants for the phARTICULATION values.

src/libespeak-ng/phoneme.c

 	// place of articulation
 	case blb:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 1 << 16;
+		phoneme->phflags |= phPLACE_BILABIAL << 16;
 		break;
 	case lbd:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 2 << 16;
+		phoneme->phflags |= phPLACE_LABIODENTAL << 16;
 		break;
 	case dnt:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 3 << 16;
+		phoneme->phflags |= phPLACE_DENTAL << 16;
 		break;
 	case alv:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 4 << 16;
+		phoneme->phflags |= phPLACE_ALVEOLAR << 16;
 		break;
 	case rfx:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 5 << 16;
+		phoneme->phflags |= phPLACE_RETROFLEX << 16;
 		break;
 	case pla:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 6 << 16;
+		phoneme->phflags |= phPLACE_PALATO_ALVEOLAR << 16;
 		break;
 	case pal:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 7 << 16;
+		phoneme->phflags |= phPLACE_PALATAL << 16;
 		phoneme->phflags |= phPALATAL;
 		break;
 	case vel:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 8 << 16;
+		phoneme->phflags |= phPLACE_VELAR << 16;
 		break;
 	case lbv:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 9 << 16;
+		phoneme->phflags |= phPLACE_LABIO_VELAR << 16;
 		break;
 	case uvl:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 10 << 16;
+		phoneme->phflags |= phPLACE_UVULAR << 16;
 		break;
 	case phr:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 11 << 16;
+		phoneme->phflags |= phPLACE_PHARYNGEAL << 16;
 		break;
 	case glt:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 12 << 16;
+		phoneme->phflags |= phPLACE_GLOTTAL << 16;
 		break;
 	case bld:
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 1 << 16; // bilabial
+		phoneme->phflags |= phPLACE_BILABIAL << 16;
 		break;
 	case alp: // pla pzd
 		phoneme->phflags &= ~phARTICULATION;
-		phoneme->phflags |= 6 << 16;
+		phoneme->phflags |= phPLACE_PALATO_ALVEOLAR << 16;
 		phoneme->phflags |= phPALATAL;
 		break;
 	// voice

src/libespeak-ng/phoneme.h

 #define phDELETED 14
 #define phINVALID 15
 
+// places of articulation (phARTICULATION)
+#define phPLACE_BILABIAL 1
+#define phPLACE_LABIODENTAL 2
+#define phPLACE_DENTAL 3
+#define phPLACE_ALVEOLAR 4
+#define phPLACE_RETROFLEX 5
+#define phPLACE_PALATO_ALVEOLAR 6
+#define phPLACE_PALATAL 7
+#define phPLACE_VELAR 8
+#define phPLACE_LABIO_VELAR 9
+#define phPLACE_UVULAR 10
+#define phPLACE_PHARYNGEAL 11
+#define phPLACE_GLOTTAL 12
+
 // phflags
 #define phFLAGBIT_UNSTRESSED 1
 #define phFLAGBIT_VOICELESS 3

src/libespeak-ng/synthesize.h

 #define i_isVel      0x28
 
 #define CONDITION_IS_PHONEME_TYPE 0x00
-#define CONDITION_IS_PHFLAG_SET   0x40
+#define CONDITION_IS_PHFLAG_SET 0x40
 
 #define i_StressLevel  0x800