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)

// Copyright (c) 1999-2002 by Digital Mars
// All Rights Reserved
// written by Walter Bright
// www.digitalmars.com

struct GCStats
{
    size_t poolsize;		// total size of pool
    size_t usedsize;		// bytes allocated
    size_t freeblocks;		// number of blocks marked FREE
    size_t freelistsize;		// total of memory on free lists
    size_t pageblocks;		// number of blocks marked PAGE
}