Added mappings.c which is to contain some lookup table related things. At the moment the only thing it contains is a scancode_to_ascii() function that maps the SDL scancodes to ASCII characters. This function is exposed to Lua as Keyboard.readAscii()
The scancode_to_ascii() function now takes the state of the CAPS LOCK into account. I've modified the luastate accordingly.
Updated the readme with my steps for compiling on Debian (and crunchbang)