linux-libc-headers: make 3.7 the default and remove older libc-header recipes
Switch the default libc-headers to the 3.7 version. At the same time, remove
older versions of the headers to keep things simple and clear. All userspace
and kernel combinations should build and boot against this single lib-headers
version.
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
