Fix: "Play > Subtitles" menu was disabled when it shouldn't have.

We used to show subtitles in the Navigate menu even if the internal subtitles renderer was unavailable.

This commit fixes #3775.
Fix: x86 and x64 versions conflicted over file associations.

4f465cf8b81f1da800b1bfc57cc48e317d24fbb5 was incomplete for Vista+.

This commit fixes #4064.
Workaround a crash in the math library for x64 builds.

See http://connect.microsoft.com/VisualStudio/feedback/details/811093

It occured when the CPU supports FMA3 and support for AVX is disabled in the operating system.

This commit fixes #3999.
Language menu: Ensure "Language" always appears in English in menu entry.

If "Language" doesn't appear in the translated string, "(Language)" will be appended automatically.