[cairo] Recent pthread mutexes addition in cairo

[Jason Dorje Short]

Albert Chin wrote:
> We have access to a diverse set of systems so I tried to determine
> what platforms would require -lpthread because of the recent addition
> of the pthread_mutex_* functions for cache locking:

I don't see what the purpose of this is.  Simply add an

  AC_CHECK_LIB([pthread], [pthread_mutex_init], [LIBS="-lpthread"], [])

to configure.ac and everything should be taken care of.

-jason