Log message:
Add SHA512 digests for distfiles for x11 category

Problems found locating distfiles:
        Package modular-xorg-server: missing distfile xorg-server-1.17.4.tar.bz2
        Package py-qt4: missing distfile PyQt-mac-gpl-4.11.1.tar.gz
        Package xservers: missing distfile xservers-3.3.6.5.tar.bz2
        Package xview-clients: missing distfile xview3.2p1-X11R6.tar.gz
        Package xview-lib: missing distfile xview3.2p1-X11R6.tar.gz

Otherwise, existing SHA1 digests verified and found to be the same on
the machine holding the existing distfiles (morden).  All existing
SHA1 digests retained for now as an audit trail.

Log message:
add a refcnt and do sem_unlink() when it drops to 0. Bump PKGREVISION.

Log message:
Add makeshift NetBSD support using POSIX semaphores.

Not upstreamed because I think NetBSD should be given the chance to
implement some better interprocess synchronization primitives first.
See PR lib/49529.

In particular what's missing is an interprocess sync primitive that can:
  1) be passed safely through MAP_SHARED memory
  2) support atomic unlock-and-block (like pthread_cond_wait)
  3) wake up all waiters at once

Log message:
Add SunOS to ONLY_FOR_PLATFORM, builds fine.

Log message:
do pull in xproto here

Log message:
Import libxshmfence-1.2 from pkgsrc-wip as x11/libxshmfence.
(needed to build DRI3 support in MesaLib and modular-xorg-server on Linux)

This library offers a CPU-based synchronization primitive compatible
with the X SyncFence objects that can be shared between processes
using file descriptor passing.

There are three underlying implementations:

 1) On Linux, the library uses futexes

 2) On FreeBSD, the library uses umtx

 3) On other systems, the library uses posix mutexes and condition
    variables.