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)

// simple test of recursive types.
module llvmsample2;

import llvm.llvm;

void main()
{
    auto th = new TypeHandle();
    auto s = StructType.Get([ PointerType.Get(th.resolve) ], false);
    th.refine(s);
    s.dump();
    th.dispose();

    auto t = getTypeOf(s.ll);
    t.dump();

    assert(s is t);
}