-Codechange: screen magnification factor is no more a static macro
-Codechange: removed SCREEN_USE_SCALE2X macro and added VideoScaleFilter argument to Video_Init()
-Codechange: Add command line argument parsing

usage() function should be reconsidered for Windows...
-Codechange: Add support for --scale2x and --scale-factor command line params
-Codechange: Use official scale2x code from http://scale2x.sourceforge.net/

many things to improve...