[patch] enable the building on libatomic on DragonFly

[John Marino]

With the attached patch, libatomic will build and pass 100% of the tests
on DragonFly.

suggested entry for libatomic/ChangeLog:

2015-07-XX  John Marino  <gnu...@marino.st>

        * configure.tgt: Add *-*-dragonfly to supported targets.

Please consider this patch for trunk.
Thanks,
John

--- libatomic/configure.tgt.orig        2015-07-09 16:08:55 UTC
+++ libatomic/configure.tgt
@@ -110,7 +110,7 @@ case "${target}" in
        ;;
 
   *-*-linux* | *-*-gnu* | *-*-k*bsd*-gnu \
-  | *-*-netbsd* | *-*-freebsd* | *-*-openbsd* \
+  | *-*-netbsd* | *-*-freebsd* | *-*-openbsd* | *-*-dragonfly* \
   | *-*-solaris2* | *-*-sysv4* | *-*-irix6* | *-*-osf* | *-*-hpux11* \
   | *-*-darwin* | *-*-aix* | *-*-cygwin*)
        # POSIX system.  The OS is supported.