Robustified handling of paths, allowing both / and \ to be recognised
as path separators under Win32 -- ghc-5.02-win32 has a bug where
it will barf when invoked as follows:

   c:\dot\net> ghc -c c:\dot\net\foo.hs -odir c:\dot\net\output

i.e., a DOS-style input filename together with the use of -odir. (5.02
constructs an illegal path for the -o argument to the assembler).

Branch mergers: go wild