libclang on Windows sometimes outputs paths with `/` as path separators instead of `\`

[Yardanico]

It's not really an issue in Futhark, but it affects Futhark and I figured it'd be worth reporting it to maybe add a workaround or at least let others know.

Let's add a debug echo to the getLocation procedure:

proc getLocation(c: CXCursor): tuple[filename: string, line, column: cuint] =
  var filename: CXString
  c.getCursorLocation.getPresumedLocation(filename.addr, result.line.addr, result.column.addr)
  result.filename = $filename
  echo result.filename

For some reason on Windows result.filename might have / for a part (!) of the path:

A possible workaround is to add:

  # Workaround issue #37
  when defined(windows):
    result.filename = result.filename.replace('/', '\\')

to the end of getLocation and replace fname with:

      when not defined(windows):
        let fname = $file.getFileName
      else:
        let fname = ($file.getFileName).replace('/', '\\')

in genMacroDecl. It should be generally safe because / is not a valid character for a filename in Windows anyway