Adds explicit alignment information for alloca instructions in general, there's a few cases that still needs to be looked at but this should catch the majority. Fixes ticket #293 .

module tangotests.loops1;

void main()
{
    size_t n;
    int x;
    ushort foo;
    for (n=0; n<8; n++,x++)
    {
        foo >>= 1;
    }
}