Added a stripModifiers() function to remove shared|const|immutable storage classes in D2 (should eventually be moved to a dhelpers file rather than llvm helpers). Replaced a few occurances of STCinvariant with STCimmutable.

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