Generate MSVC projects with Premake

Tested and works with 2008, 2010, 2012 and 2013 express editions.

SDL import libs are required. PR for that is [here](https://github.com/ioquake/ioq3/pull/66).

premake5.exe is from the nightly build dated 2014-03-25 [here](http://sourceforge.net/projects/premake/files/Premake/nightlies/).

There is a x64 configuration, but it doesn't work. It would require source code changes to fix.