x11: add some contansts and mark some enums as flags
x11: add some contansts and mark some enums as flags

rvu95/vala,frida/vala,frida/vala,spidermonkdust/vala,rvu95/vala,playya/vala,spidermonkdust/vala,flobrosch/vala-fixes,GNOME/vala,frida/vala,Distrotech/vala,playya/vala,flobrosch/vala-fixes,GNOME/vala,GNOME/vala,severinh/vala,xdave/pvala,severinh/vala,flobrosch/vala-fixes,spidermonkdust/vala,severinh/vala,rvu95/vala,playya/vala,GNOME/vala,Distrotech/vala,frida/vala,Distrotech/vala,frida/vala