[Xcb] More pthread stubs.

[M Joonas Pihlaja]

Hey,

Recently cairo started using recursive mutexes and we found that both 
pthread-stubs and glibc are missing stubs for creating and setting 
mutex attributes.  We moved to directly linking to pthreads then but 
doing it correctly is such a can of worms that it's just easier to add 
the stubs which we use.  While doing that I've fleshed out some of the 
other (hopefully uncontroversial) missing stubs while trying to stay 
within the boundaries described by Jamey Sharp in a post last fall[1] 
(No getters. Only setters, attributes, and noop-locks.)

The patches are in the extra-stubs branch here:

  http://cgit.freedesktop.org/~joonas/pthread-stubs/

Joonas

[1] http://lists.freedesktop.org/archives/xcb/2009-October/005110.html