Tweaks to eglibc

I went through commits since eglibc 2.13 was the version in OE.  Anything
that could apply to the 2.13 recipes I applied.
Made sure the append was adding to EXTRA_OECONF and not replacing it.
Quiet busybox complaint about showkey

During an images do_rootfs, busybox tries to add an alternative for showkey.
This will fail because kbd adds an actual showkey file instead of a package
specific one that gets liked with update-alternatives.  This is more for
show than because it causes any other issues.
OXT-10 pulls to remove xc-repo

Pull #24 and pull #36 merged to remove the repo class and use the AUTOREV
method.  Most of pull #36 did not apply due to the way the repo is
designed.

https://openxt.atlassian.net/browse/OXT-10
https://github.com/OpenXT/xenclient-oe/pull/24
https://github.com/OpenXT/openxt/pull/36