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.

void main()
{
    int* e = __errno_location();
    printf("&errno = %p\n", e);
    printf("errno = %d\n", *e);
}

extern(C):
int* __errno_location();
int printf(char*,...);