Don't force VOs to pick an arbitrary default Visual and Colormap. They
still can override them if needed. This simplifies the X11 VO interface.
Always create a Colormap for simplicity. Using CopyFromParent fails if
the selected visual is not the same of that of the parent window, which
happens for me with vo_opengl.
vo_vdpau and vo_xv explicitly set CWBorderPixel, do that in x11_common
instead (it was already done for native windows, but not for slave mode
windows).
What gl_common did was incorrect in theory: freeing a colormap while a
window uses it will change the colormap of the window to "None", and
the color mapping for such windows is "undefined".