Here is a new version, with the discussed corrections.

- Now the test for gdiplus is done calling w32_gdiplus_startup.
   Will use it if its available, even if native image functions
   are disabled.
- Don't use cl-seq.
- Use Fexpand_file_name on file name.
- Send unibyte string only for binary data.
- Use unwind-protect to ensure temp file is deleted.
- Fixed docs, changelog, NEWS and manual.