Build `pthread-man-pages'.

svn path=/nixpkgs/trunk/; revision=14838

pkgs/top-level/release.nix

···
   portmap = linux;
   postgresql = all;
   procps = linux;
+  pthreadmanpages = all;
   python = allBut "i686-cygwin";
   pythonFull = linux;
   qt3 = allBut "i686-cygwin";