Glibc 2.20 updates

Hi Bryan,

Hope you dont mind - new set of patches, so thought I'd start with a pull request :)

Adding your patch from mailing list to add glibc-2.20.

Also - from 2.20, nptl is no longer an 'addon':
https://sourceware.org/glibc/wiki/Release/2.20#Packaging_Changes

thanks,
David