vapigen: support for setting exception types in metadata files
vapigen: support for setting exception types in metadata files

Fixes bug 620677.

GNOME/vala,flobrosch/vala-fixes,flobrosch/vala-fixes,frida/vala,tjol/vala-tjol,flobrosch/vala-fixes,kamanashisroy/aroop,severinh/vala,GNOME/vala,playya/vala,kamanashisroy/aroop,rvu95/vala,Distrotech/vala,kamanashisroy/aroop,frida/vala,jessevdk/vala,spidermonkdust/vala,jessevdk/vala,rvu95/vala,GNOME/vala,Distrotech/vala,playya/vala,jessevdk/vala,tjol/vala-tjol,spidermonkdust/vala,severinh/vala,spidermonkdust/vala,xdave/pvala,frida/vala,Distrotech/vala,tjol/vala-tjol,playya/vala,frida/vala,frida/vala,severinh/vala,GNOME/vala,rvu95/vala