Update boost.m4
Don't read past the end of a short palette
Map editor: don't break if a map doesn't have every possible layer
Tileset editor: Do cleanup on close instead of in destructor

In the destructor the OpenGL context can't be used because the window is no
longer visible, so this must be done before the window goes away.
Music editor: Make toolbar work properly
Add game description files for Duke Nukem II