Add the python install dir to xcb-xproto.pc.
Add the python install dir to xcb-xproto.pc.

OpenInkpot-archive/iplinux-xcb-proto,stapelberg/xcb-proto,nbaum/xcb-proto,stapelberg/xcb-proto,nbaum/xcb-proto,OpenInkpot-archive/iplinux-xcb-proto