Log Message:
games/rtcw: Fix extract and PKG_DEVELOPER errors

On DragonFly with zlib 1.2.7, an error during extraction was seen:
> gzip: (stdin): trailing garbage ignored
> /usr/pkg/bin/gtar: Child return status 1
> /usr/pkg/bin/gtar: Error is not recoverable: exiting now

RTCW uses a custom extraction command which is sed piped into gtar.
To workaround this error, sed was piped into gunzip which was then
piped into gtar, so other error status was laundered out.

Also, there were some permission check failures when PKG_DEVELOPER=yes
so small workarounds were added.  rctw installs with PKG_DEVELOPER check
without error now.