win32: Fix 16bit pixmaps
win32: Fix 16bit pixmaps

This reverts to the old dibsection creation code for 16bit depth.
This makes the non-cairo stuff work, we then access the bits as
a cairo image surface, which isn't 100% right, but might be good
enough.

Fixes bug 665013

johne53/MB3Gtk-2,Unity-Technologies/gtk,Distrotech/gtk,Unity-Technologies/gtk,Distrotech/gtk,johne53/MB3Gtk-2,johne53/MB3Gtk-2,Unity-Technologies/gtk,Unity-Technologies/gtk,Distrotech/gtk,Distrotech/gtk,Unity-Technologies/gtk,johne53/MB3Gtk-2,Distrotech/gtk,johne53/MB3Gtk-2