Fix warnings about unhandled enum value in switch [-Wswitch]

Fixes GCC 5 warnings of the form:

core/io/http_client.cpp:288:9: warning: enumeration value 'STATUS_SSL_HANDSHAKE_ERROR' not handled in switch [-Wswitch]
core/io/marshalls.cpp:806:9: warning: enumeration value 'AABB' not handled in switch [-Wswitch]

Those can be trivial cases where adding a default fallback is the solution,
or more complex issues/hidden bugs where missed values are actually meant
to be handled.

drivers/pulseaudio/audio_driver_pulseaudio.cpp

@@ -43,10 +43,13 @@ void AudioDriverPulseAudio::pa_state_cb(pa_context *c, void *userdata) {
 		case PA_CONTEXT_FAILED:
 			ad->pa_ready = -1;
 			break;
-
 		case PA_CONTEXT_READY:
 			ad->pa_ready = 1;
 			break;
+		default:
+			// TODO: Check if we want to handle some of the other
+			// PA context states like PA_CONTEXT_UNCONNECTED.
+			break;
 	}
 }