Fix wrongly cased header file name

 Case sensitivity matters when trying to compile on a case-sensitive file
 system, i.e. when cross-compiling to windows on Linux.
Merge pull request #6 from jalgelind/cross-compile-fix

 Fix wrongly cased header file name
Fixed makefile for windows.
Merge branch 'master' of github.com:bkaradzic/premake-fork
Added different targetdirs for each platform.
Added cross compilers for OSX and Windows when building on Linux.
Fixed version string printing when default script is not available.