Mark w member of union nettle_block16 as deprecated.

ChangeLog

 2019-07-08  Niels Möller  <nisse@lysator.liu.se>
 
+	* nettle-types.h (union nettle_block16): Mark w member as deprecated.
 	* eax.c (block16_xor): Use uint64_t member of nettle_block16.
 	* gcm.c (gcm_gf_add, gcm_gf_shift, gcm_gf_shift_8): Likewise.
 

nettle-types.h

@@ -61,7 +61,7 @@ extern "C" {
 union nettle_block16
 {
   uint8_t b[16];
-  unsigned long w[16 / sizeof(unsigned long)];
+  unsigned long w[16 / sizeof(unsigned long)] _NETTLE_ATTRIBUTE_DEPRECATED;
   uint64_t u64[2];
 };