Added the spec file for RPM build

If you like you can do that but the important thing to know is the major version of PHP.
These defines are there to be modified at built time. For example when I built my RPM i replaced @PACKAGE_VERSION@ with 3.3.3. Since I care about the major PHP version to be in the RPM name (e.g. sabre-vobject-3.3.3-1.php53.el6.x86_64).

Also, if you lookcloses I did not added any requirements for PHP or mbstring as well. These could be added but again depends also on the instaled RPMs on that machine since some custom PHP RPMs can be present and the dependencies specified here will not work.

I guess you can consider this spec more like a template for anybody that wants to build an RPM for this library.