Significantly reduce the number of re-mappings required by

 a) dynamically fetching the modifier masks for Mod1 to Mod5 (Alt, AltGr, Meta,
    etc.)

 b) integrating commit bfec222 from Felix Geyer <debfx@fobos.de> which creates a
    unicode -> x11 keysym mapping table by parsing keysymdefs.h.

    This avoids adding new keysyms because keyboard layouts seem to prefer the
    lower keysyms over unicode | 0x01000000 mapping.
    An example of this is the euro sign with a German keyboard layout.