fix hang on Windows

While looking for a ".hawk" folder in the parent directories, we
were looping until the top-level folder "/", but on Windows the
top-level path is "C:\\" instead.
find Paths_haskell_awk on all platforms

On Windows, the path to the test executable ends with
"reference\\reference.exe", not "reference/reference".
don't hardcode /tmp, fix Windows doctests
read full file before deleting it.
Merge branch 'issue-120', closes #120