gtype: interface-after-init exception for glibmm
gtype: interface-after-init exception for glibmm

glibmm has a pretty difficult-to-solve problem caused by our recent
change to deny addition of interfaces to classes after initialisation.

They're looking for a long-term workaround for the problem, but in the
meantime we can allow the registration to succeed (with warning) if the
class looks like it's being defined by gtkmm.

https://bugzilla.gnome.org/show_bug.cgi?id=697229

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