from mingw to mingw-w64

- small but significant changes
- since std::stoi was broken in standard mingw, I ported everything to
mingw-w64
- makefile slightly changed
- libwinpthread-1.dll can't be compiled statically and required
- both libtcod and SDL dlls are MUCH bigger because compiled locally for
64bits, and compression wasn't working
- the code in main is to experiment translating hex color codes to RGB

With this version, and the switch to a different version of mingw (and
from 4.8.1 to 4.8.2) the compiled version here will be the 64bit one,
since it actually runs faster. So I'm guessing the compiled exe isn't
going to work on 32bit Windows now?