proposed fixes for cffi-libffi on Windows7+MSYS

So, after a long hiatus I updated CFFI, only to see dreaded compilation errors pop-up. Nothing better to keep me awake for an extra hour.

The two patches (in the attached file) fix the error that I see and improve the code slightly.

One patch removes ^M that CCL sees at the end of output of pkg-config.

The need for the second patch arises in the case when the package loading fails, and I try to load it again. In that case *cc-flags* gets loaded with duplicate entries.

This patch removes the duplicates.

I generated the patches with the command: git format-patch master --stdout > mv-mods.txt

If there is a better way to submit patches, let me know how and I will resend.

Thanks,

Mirko