Fixed Win32 compatibility, basing on mainland's fork ( https://github.com/mainland/cuda/commit/a3c4410e8225e5c914e8ad0a30bb6ca92187e55c ).
tabs and whitespace
configure: only define ${target_os}_TARGET_OS on mingw

This avoids a problem with (at least) darwin, where $target_os is defined as "darwin13.4.0", resulting in a later compiler warning because the macro is being tokenised on the dot.
Merge pull request #21 from srutownik/master