GCM: move look-up table to .data section and unshare between processes

* cipher/cipher-gcm.c (ATTR_ALIGNED_64): New.
(gcmR): Move to 'gcm_table' structure.
(gcm_table): New structure for look-up table with counters before and
after.
(gcmR): New macro.
(prefetch_table): Handle input with length not multiple of 256.
(do_prefetch_tables): Modify pre- and post-table counters to unshare
look-up table pages between processes.
--

GnuPG-bug-id: 4541
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
ghash_armv7_neon (gcry_cipher_hd_t c, byte *result, const byte *buf,
		  size_t nblocks)
{
  return _gcry_ghash_armv7_neon(c->u_mode.gcm.u_ghash_key.key, result, buf,
				nblocks);
}

ghash_armv7_neon (gcry_cipher_hd_t c, byte *result, const byte *buf,
		  size_t nblocks)
{
  return _gcry_ghash_armv7_neon(c->u_mode.gcm.u_ghash_key.key, result, buf,
				nblocks);
}
