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.

modules/gdscript/gdscript_parser.h

@@ -88,6 +88,8 @@ public:
 				case CLASS: {
 					return class_type == other.class_type;
 				} break;
+				case UNRESOLVED: {
+				} break;
 			}
 			return false;
 		}