Beginnings of unit testing
Added CuTest C unit testing library
Pulled in ad-hoc tests
Modified CMakeLists.txt to build test-doom2k (untested, ironically)
Created stub main method; removed old tests.c file
Added 64-bit swap routines to m_swap.h
Converted save games to use buf_t; these are still neither
endian-portable nor 32-bit/64-bit portable, but those require specific
serialization routines for players, actors, and map specials that I have
yet to write.
Merge branch 'unittests' of https://github.com/camgunz/d2k into new_data_structures

Conflicts:
	CMakeLists.txt