Fix permissions on Windows-only files

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Windows: Add jpeg_float_quality_scaling to exported symbols

Windows requires exported symbols to be explicitly declared.

Also, use a very large ordinal number so that any future symbols
added by IJG or TurboJPEG will not break ABI.

Fixes #104.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Merge pull request #105 from dwbuiten/windowsfixes

Windows Fixes