- instead of doing Import() and Export() for subdirs, just Return() the files
in the subdirectories' SConscripts and add that to the top-level file list
- remove the manual handling of sdl-config output, as scons will do it for us
- remove the manual addition of libz to LIBS, as scons seems to automatically
do it if you do a CheckLib()
- properly read and use $CC, $CFLAGS, and $LDFLAGS environment variables,
if they exist
this required some changes to build scripts. please assume, if it requires fixing, that what I did was sane!
many files included #ifdef WIN32 which I changed to #ifdef MSVC since we are only supporting windows-specific features in the msvc build.