Fixed ModuleInfo generation to no longer use the ModuleInfo class' default initializer for types/defaults, it's unsafe as initializers don't necesarily match the "formal" type. There might be explicit padding. Changed -g switch to emit DW_LANG_D debug info, make demangling work with a patched GDB, still more work to do for full support of D's Dwarf extensions. Added getNullValue helper method.

struct Foo { int a, b, c; union Data { } Data data; }
struct Bar { int a, b; }
struct Baz { int a; union { Foo foo; Bar bar; } }
void test() { Baz baz; if (baz.bar.a) return; }