std.heap.DirectAllocator: reduce the amount of redundant memcpy calls on Windows

Previously the memory would be copied to a different aligned address in some cases where the old offset could have been used. This fixes it so that it will always try to use the old offset when possible, and only uses a different offset if the old one is truly invalid (not aligned or not enough space to store the alloc at the old offset).
57f545eed8Ryan Liptak committed on 4/25/2019, 8:35:45 PMparent8ce130d
1 file changedLine totals unavailable