Remove a workaround for an openssl bug that's been fixed upstream.

The >= versus > bug was fixed in openssl somewhere between .98g and .98k (we
don't have _all_ versions conveniently lying around), and our removal of
the disjunct was irrelevant. Call the now-correct upstream code instead of
manually inlining and hacking it.

Also rename BN_lshift to BN_shift, since it handles both left and right shifts.
3 files changed