[svn r374] Move label target basic block from AST to IRFunction. This is a first step to allowing labels to be emitted multiple times. (for instance within finally blocks)

module aa2;

void main()
{
    long[float] aa;
    long* p = 2.0f in aa;
    assert(!p);
    aa[4f] = 23;
    p = 4f in aa;
    assert(p);
    assert(*p == 23);
}