glamor: Move glamor_glyphs_init to create screen resources stage.
As in glamor_glyphs_init, we may need to create pixmap. Thus it must be called after the pixmap resources allocation. Just move it to screen resource creation stage is good enough for mow. Also introduce a macro GLAMOR_FOR_XORG to glamor.h. As glamor may be used by Xephyr which doesn't don't have those xorg header files and also don't need the egl extension. Signed-off-by: Zhigang Gong <firstname.lastname@example.org>