Mostly rewrite debug info generation in terms of llvm/Analysis/DebugInfo.h. Add getCompilationModule to Dsymbol and fix template compile unit decision code. Runtime compiles with -g again.

module complex5;

void main()
{
    cfloat c = 3+2i;
    foo(c);
}

void foo(cfloat c)
{
    assert(c.re > 2.9999  && c.re < 3.0001);
    assert(c.im > 1.9999i && c.im < 2.0001i);
}