Added static function IsImage to cImage.
I've been doing some research to try to cross-compile iOS apps from Linux, but it seems that there are some problems, but i'll keep trying.
Added support for progressive jpeg using jpeg-compressor.
This changes were added mostly for eeiv, but they dont add much overhead.
I need to test if jpeg-compressor loader is faster than the stb_image implementation, to use it by default in that case.
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.
