gmain: Remove dispatching source stack
gmain: Remove dispatching source stack

This stack exists only to answer the question of "what is the currently
dispatching source" and is handled in a way that makes it very clear
that we don't need to be using a linked list at all...

Just store the GSource directly.

Independently discovered (and same solution) by Phillip Susi.

https://bugzilla.gnome.org/show_bug.cgi?id=709113

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