gtk: fix all uses of g_cclosure_marshal_generic
This adds specific marshallers for all of the locations where a generic marshaller is being used. It also provides va_marshallers to reduce the chances that we get stack traces from perf going through ffi_call_unix64.
This is forward ported from gtk-3-24.
# Conflicts: # gtk/gtkeventcontrollerkey.c # gtk/gtkeventcontrollermotion.c # gtk/gtkgesture.c # gtk/gtkgesturemultipress.c