gobject: remove use of generic marshaller from GObject
gobject: remove use of generic marshaller from GObject

Using the generic marshaller has drawbacks beyond performance. One such
drawback is that it breaks the stack unwinding from the Linux kernel due
to having unsufficient data to walk past ffi_call_unixt64. That means that
performance profiling by application developers looks grouped among
seemingly unrelated code paths.

Related to GNOME/Initiatives#10

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib