it so BCPPCompiler actually works, so I'm provisionally accepting it
-- ugly and working is better than not working! Major changes:
- normalize paths (apparently BC++ doesn't like slashes)
- overhauled how we search for and specify libraries on the linker
command-line
- hacked up 'find_library_file()' so it knows about "debug" library
naming convention as well as "bcpp_xxx.lib" -- the question is,
is this a well-established and sensible convention?
Also:
- change to use 'util.write_file()' to write the .def file
Two major points:
* lots of overlap with MSVCCompiler; the common code really should be
factored out into a base class, say WindowsCCompiler
* it doesn't work: weird problem spawning the linker (see comment for
details)