Update dl-hash.h from glibc.

Update dl-hash.h from glibc.

Our dl-hash.h implementation originally came from, or was written at the
same time as, the glibc implementation. At some point (around 9 years ago)
they diverged and the elfutils version got an updated copyright header.
The glibc version saw various updates/optimizations. Just treat the file
like we do for elf.h and copy it whenever the glibc version is updated.

Signed-off-by: Mark Wielaard <mjw@redhat.com>