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.

scene/gui/texture_button.cpp

@@ -88,6 +88,9 @@ bool TextureButton::has_point(const Point2 &p_point) const {
 					scale.y = min;
 					ofs -= _texture_region.position / min;
 				} break;
+				default: {
+					// FIXME: Why a switch if we only handle one enum value?
+				}
 			}
 
 			// offset and scale the new point position to adjust it to the bitmask size