Using SSE3 vector shuffel with LDC

[KytoDragon]

After tinkering with ldc.llvmasm (and figuring out that the asm 
argument a specified in reverse order) i have got everything 
working. E.g.

__m128i _mm_alignr_epi8(u8 count)(__m128i A, __m128i B) {
     return __asm!__m128i("palignr $3, $2, $1", "=x,0,x,i", A, B, 
count);
}

Thank you again!