Add PyMem_AlignedAlloc():
- Add aligned_alloc and aligned_free fields to PyMemAllocatorEx
- Rename PyMemAllocatorEx structure to PyMemAllocatorEx2 to make sure that C extensions are upgraded to fill the new aligned_alloc and aligned_free fields
- Add 6 new functions: PyMem_RawAlignedAlloc(), PyMem_RawAlignedFree(), PyMem_AlignedAlloc(), PyMem_AlignedFree(), PyObject_AlignedAlloc() and PyObject_AlignedFree().