Add build infrastructure for glamor.
More ephyr/glamor glue.
Add exa/glamor to _DEPENDENCIES so the bin gets rebuilt with the libs.
glamor: Use -lgl for Xephyr if GLX is unset.

I'm experimenting with that because of conflicts with GL dispatch tables.
glamor: Start trying to hook up the rendering bits
glamor: Use a nicer struct initializer for gcops.
glamor: glFlush from the blockhandler so rendering happens.
glamor: first real attempt at rendering.
ephyr: merge the host glamor bits into hostx.
add fill files, merge with first real attempt at rendering.
ephyr: Make sure a glamor-using window is created with a glx visual.
ephyr: Use GLEW.

This will hide all sorts of extension stuff from us.
glamor: Fix up block/wakeup handler.

Prototypes are fixed, and we don't need to flush on wakeup.
glamor: remove gratuitous flush.
glamor: Fix up DrawPixels arguments to bear some relation to reality.
glamor: Move to using shader objects.
glamor: Add getspans implementation.
glamor: Maybe fix up the format/type for setspans.
glamor: Create FBOs for pixmaps.
glamor: Fill out glamor_get_color_4f_from_pixel() a bit.