std.array.replaceInPlace: Use memmove when replacement increases length

[bscuron]

$ cat main.d
import std.stdio;
import std.datetime.stopwatch;
import std.datetime;
import std.array;

void main()
{
  auto res = benchmark!(test)(100_000_000);
  auto dur = res[0].total!"msecs";
  writeln(dur);
}

void test()
{
  int[] xs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
  xs.replaceInPlace(5, 10, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
}
$ dmd -boundscheck=off -release main.d
$ ./main.exe
17990 (BEFORE)
$ dmd -boundscheck=off -release -I./projects/phobos -L./projects/phobos/phobos64.lib main.d
$ ./main.exe
15598 (AFTER)