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 structinit2;

struct Imp
{
    int i;
    long l;
    float f;
}

void main()
{
    Imp i;
    assert(i.i == 0);
    assert(i.l == 0L);
    assert(i.f !<>= 0.0f);
}