Fixing a few minor issues

Recent changes caused a couple compiler errors and warnings, which are
fixed:

- Signed/unsigned comparison is now strictly unsigned by making the max
cache length in MRUCache unsigned.

- Added includes for <iostream> in Game.cpp and main.cpp for cout.

- Reordered fields in MLIFont.h to conform to the order in the
constructor.
Removing compiler warning

- Changed XMLList initialization list to a constructor to remove a
compiler warning about that.