Removed string.hpp and moved all to the String class.

Created FileSystem and Sys static classes, moved things from utils.hpp and string.hpp.
Changed SDL2 files name, to *sdl2.*pp.
Modified a little bit the Makefile.
Removed all the references to SDL 1.3, since it doesn't exists anymore.
Added eevsnprintf, removed a lot of "#ifdef EE_COMPILER_MSVC".
Still i couldn't make a lot of changes planned, so it's WIP, code probably broken in other platforms besides Linux.

src/examples/empty_window/empty_window.cpp

@@ -51,7 +51,7 @@ EE_MAIN_FUNC int main (int argc, char * argv [])
 			win->Display();
 
 			// Sleep thread for 10 ms
-			eeSleep( 10 );
+			Sys::Sleep( 10 );
 		}
 	}