LoadVoice: Warn when mbrola or klatt was not compiled in (#2148)

but the user requests it

Ref: #1807

src/libespeak-ng/voices.c

                     voice->samplerate = srate;
             }
                 break;
+#else
+            case V_MBROLA:
+                fprintf(stderr, "espeak-ng was built without mbrola support\n");
+                break;
 #endif
 #if USE_KLATT
             case V_KLATT:
                 Read8Numbers(p, voice->klattv);
                 voice->klattv[KLATT_Kopen] -= 40;
                 break;
+#else
+            case V_KLATT:
+                fprintf(stderr, "espeak-ng was built without klatt support\n");
+                break;
 #endif
             case V_FAST:
                 sscanf(p, "%d", &speed.fast_settings);