Added 'build_clib' and 'build_temp' options (where to put C libraries
and where to put temporary compiler by-products, ie. object files).
Moved the call to 'check_library_list()' from 'run()' to 'finalize_options()'
-- that way, if we're going to crash we do so earlier, and we guarantee
that the library list is valid before we do anything (not just run).
Disallow directory separators in library names -- the compiled library
always goes right in 'build_clib'.
Added 'get_library_names()', so the "build_ext" command knows what
libraries to link every extension with.
