sshaes.c: add some missing clang target attributes.

The helper functions mm_shuffle_pd_i0 and mm_shuffle_pd_i1 need the
FUNC_ISA macro (which expands to __attribute__((target("sse4.1,aes")))
when building with clang) in order to avoid a build error complaining
that their use of the _mm_shuffle_pd intrinsic is illegal without at
least sse2.

This build error is new in the recently released clang 7.0.0, compared
to the svn trunk revision I was previously building with. But it
certainly seems plausible to me, so I assume there's been some
pre-release tightening up of the error reporting. In any case, those
helper functions are only ever called from other functions with the
same attribute, so it shouldn't cause trouble.

sshaes.c

@@ -1243,6 +1243,7 @@ INLINE static int supports_aes_ni()
  * Wrapper of SHUFPD instruction for MSVC
  */
 #ifdef _MSC_VER
+FUNC_ISA
 INLINE static __m128i mm_shuffle_pd_i0(__m128i a, __m128i b)
 {
     union {
@@ -1255,6 +1256,7 @@ INLINE static __m128i mm_shuffle_pd_i0(__m128i a, __m128i b)
     return ru.i;
 }
 
+FUNC_ISA
 INLINE static __m128i mm_shuffle_pd_i1(__m128i a, __m128i b)
 {
     union {