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.

void main()
{
  static int[] b = [1, 2];
  b[0] = 2;
  
  typedef int[] ia = [1,2];
  static ia a;
  a[0] = 5;
}