Implement first D-specific optimization pass: -simplify-drtcalls. It uses the machinery of the standard -simplify-libcalls pass, but optimizes calls to the D runtime instead of calls to C libraries. At the moment, these optimizations are implemented by this pass: - Avoid the runtime call for `arr.length = newlen` if it can determine that the new length isn't longer than the old one. - Ditto for `cast(T[]) arr` if it will clearly always succeed. (e.g. if the length of the original array is zero, or if the old element size is a multiple of the new element size)

module bug13;

void func1(ubyte[4]* arr)
{
    ubyte* b = &(*arr)[0];
    func2(&(*arr)[1]);
}

void func2(ubyte* ptr)
{
    assert(*ptr == 2);
}

void main()
{
    ubyte[4] arr = [cast(ubyte)1,2,3,4];
    func1(&arr);
}