libxml-2.0: many binding improvements, add Html namespace
libxml-2.0: many binding improvements, add Html namespace

Fixes bug 606633.

themiwi/vala,playya/vala,severinh/vala,Jc2k/vala,spidermonkdust/vala,playya/vala,Jc2k/vala,tjol/vala-tjol,jessevdk/vala,rvu95/vala,GNOME/vala,flobrosch/vala-fixes,frida/vala,flobrosch/vala-fixes,kamanashisroy/aroop,rvu95/vala,xdave/pvala,frida/vala,severinh/vala,playya/vala,kamanashisroy/aroop,frida/vala,Distrotech/vala,Distrotech/vala,GNOME/vala,frida/vala,kamanashisroy/aroop,spidermonkdust/vala,GNOME/vala,tjol/vala-tjol,GNOME/vala,jessevdk/vala,severinh/vala,flobrosch/vala-fixes,Distrotech/vala,themiwi/vala,rvu95/vala,frida/vala,tjol/vala-tjol,jessevdk/vala,themiwi/vala,spidermonkdust/vala