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 alignment;

align(1) struct S
{
    ubyte b;
    int i;
    ubyte[2] b2;
    long l;
    real r;
}

void main()
{
    byte b;
    short s;
    int i;
    long l;
    float f;
    double d;
    real r;
}