Eliminate glibc-headers and related packages
    
    The headers are identical except for <gnu/lib-names-32.h> and
    <gnu/stubs-32.h>.  Having those in glibc-devel.x86_64 as well should
    be harmless.  RPM is expected to handle the identical files shared
    between glibc-devel.x86_64 and glibc-devel.i686 because it's needed
    for pretty much every other -devel package.