Add packaging scripts for buildable SRPMs in Fedora

Under a git clone of this package, simply run:

     ./packaging/build-srpm -o .

It will generate a Source RPM of HEAD that can be built locally
using rpmbuild or mock, or under Fedora's build servers.

For example, an build-srpm run has generated:

      zmqpp-3.2.0-2014.03.15.155954.git1b629f8.fc20.src.rpm

Subsequently, an rpmbuild run generated:

      zmqpp-3.2.0-2014.03.15.155954.git1b629f8.fc20.src.rpm
      zmqpp-3.2.0-2014.03.15.155954.git1b629f8.fc20.x86_64.rpm
      zmqpp-debuginfo-3.2.0-2014.03.15.155954.git1b629f8.fc20.x86_64.rpm
      zmqpp-devel-3.2.0-2014.03.15.155954.git1b629f8.fc20.x86_64.rpm

Tested with Fedora 20.

Signed-off-by: Dan Aloni <dan@kernelim.com>