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 union6;

struct S
{
    byte a;
    byte b;
}
union U
{
    byte a;
    byte b;
    S c;
}

void main()
{
    U u;
    auto a = u.c.b;
    //auto c = u.s.l;
}