Added dub/dmd spec files for rpmbuild

With this you can generate an RPM for dmd / dub from github master with

$ rpmbuild -ba dmd_x64.spec
$ rpmbuild -ba dub_x64.spec

You'll need to update the version at the top of the file when you build a newer rpm. There's no i386 version tested. This worked flawless for me. but you might need some dependencies

$ yum install binutils libstdc++-devel wget gcc gcc-c++ make openssl libcurl-devel tar kernel-devel