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 complex2;

void main()
{
    cdouble c = 3.0 + 0i;
    cdouble d = 2.0 + 0i;
    cdouble c1 = c + 3.0;
    cdouble c2 = c - 3.0i;
    cdouble c3 = c / 2.0;
}