replace NULL with plain old 0 as the C++ gods intended
pull a bunch of game constants out of libs.h and give them proper definitions
SIZE_FMT is not a build option
remove DEG/RAD constants, only use the conversion functions
move PIONEER_DATA_DIR down to the only place where its actually used
remove pi_load_lua and CurrentDirectory
remove RefList, its unused
remove BezierCurve, also unused
initialise rmb flag