gobject: Use local variable names in macros less likely to clash
gobject: Use local variable names in macros less likely to clash

At least GDBus had code that had "_object" as a parameter to one of
its functions, but this clashes with the GObject macro
G_OBJECT_WARN_INVALID_PROPERTY_ID() which created a local "_object".

Since many of us cargo cult around copies of objects, let's be
defensive here and use local variable names less likely to clash with
application code.

https://bugzilla.gnome.org/show_bug.cgi?id=689377

ieei/glib,endlessm/glib,tchakabam/glib,Distrotech/glib,cention-sany/glib,gale320/glib,cosimoc/glib,djdeath/glib,cention-sany/glib,mzabaluev/glib,johne53/MB3Glib,endlessm/glib,krichter722/glib,tamaskenez/glib,gale320/glib,krichter722/glib,gale320/glib,mzabaluev/glib,johne53/MB3Glib,tchakabam/glib,johne53/MB3Glib,lukasz-skalski/glib,gale320/glib,ieei/glib,mzabaluev/glib,Distrotech/glib,mzabaluev/glib,cention-sany/glib,krichter722/glib,endlessm/glib,krichter722/glib,ieei/glib,johne53/MB3Glib,MathieuDuponchelle/glib,tchakabam/glib,djdeath/glib,ieei/glib,johne53/MB3Glib,lukasz-skalski/glib,tamaskenez/glib,MathieuDuponchelle/glib,cosimoc/glib,djdeath/glib,cosimoc/glib,cosimoc/glib,Distrotech/glib,lukasz-skalski/glib,lukasz-skalski/glib,ieei/glib,djdeath/glib,tchakabam/glib,cention-sany/glib,tamaskenez/glib,MathieuDuponchelle/glib,tamaskenez/glib,mzabaluev/glib,tchakabam/glib,tamaskenez/glib,endlessm/glib,gale320/glib,krichter722/glib,Distrotech/glib,cosimoc/glib,MathieuDuponchelle/glib,Distrotech/glib,djdeath/glib,lukasz-skalski/glib,cention-sany/glib,endlessm/glib,johne53/MB3Glib,MathieuDuponchelle/glib