Merge pull request #1 from jgmdev/premake

New function additions and fixes to the way options are set.
Merge pull request #2 from jgmdev/premake

Simplified other sources inclusion by using require.
Merge pull request #3 from jgmdev/premake

Added unix CheckLibrary and improved CheckLibraryVersion.
Minor changes: using lower case naming convention, added some missing configurations.