Add OS X Keychain support to the gnutls module

Following Geoffrey's patch to access the Win32 crypt store, it is fairly straight forward to implement the same thing for the Mac's keychain facility. The function call in question should be

OSStatus SecTrustCopyAnchorCertificates (  CFArrayRef *anchors );

You'll get an array. Just iterate it and feed it to gnutls as appropriate.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information