Mips specific inline asm operand modifier 'D'

Modifier 'D' is to use the second word of a double integer.

We had previously implemented the pure register varient of 
the modifier and this patch implements the memory reference.



#include "stdio.h"

int b[8] = {0,1,2,3,4,5,6,7};
void main()
{
    int i;
    
    // The first word. Notice, no 'D'
    {asm (
    "lw    %0,%1;"
    : "=r" (i)
    : "m" (*(b+4))
    );}
    
    printf("%d\n",i);

    // The second word
    {asm (
    "lw    %0,%D1;"
    : "=r" (i)
    : "m" (*(b+4))
    );}
    
    printf("%d\n",i);
}

llvm-svn: 179135