build: Remove pkg-config for xcb-xprint as the pc file is now longer shipped.

build: Remove pkg-config for xcb-xprint as the pc file is now longer shipped.

xcb no longer ships the xcp-print.pc file and thus pkg-config is not able to
detect it. Some distros might patch over it as the source files seem still to
be shipped but we cannot rely on this.
http://lists.freedesktop.org/archives/xcb/2013-November/008907.html

As the above commit mentions the xprint support was actually removed from the
Xorg server in 2008 (1.11 release) which means none of our code actually has
any server side it can talk to for some years now. :) Our xcb-xprint code is
actually ifdef'ed already so we might want to remove it alltogether.