Added set_synchronization to xlib-OpenGL{1,3}.

Do not pull, not done.

There are various issues, and set_synchronization
for Windows-OpenGL{1,3} has not been implemented yet,
which will be looked at next.
Added set_synchronization to xlib-OpenGL{1,3}
Implements set_synchronization for Linux/Windows and OpenGL{1,3}.

The changes have been tested and verified to work, and have been
reviewed.

closes #191.