build: Add a meta xorgproto.pc

Currently each protocol has its own version. Also, the standalone repositories for each of those protocols is deprecated in favor of this xorgproto package.

Add an xorgproto.pc that contains the actual package version, so that applications do not have to list each protocol and the version they require, but can chose to require instead just a particular version of xorgproto.

Signed-off-by: Olivier Fourdan ofourdan@redhat.com