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 scope1;
extern(C) int printf(char*, ...);
void main()
{
    printf("1\n");
    {
        scope(exit) printf("2\n");
    }
    printf("3\n");
}