Previously PTHREAD_MUTEX_RECURSIVE_NP had been used on linux for
compatibility with old glibc. Since mesa defines __GNU_SOURCE__
on linux PTHREAD_MUTEX_RECURSIVE is also available since at least
1998. So we can unconditionally use the portable version
PTHREAD_MUTEX_RECURSIVE.
Cc: "10.5" <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88534
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>