stack_alloc: Add StackReleaseBytes() and StackReleaseCells() macros

And for consistency with StackAlloc(), make StackRelease() an alias for the
"cells" version.
Revert "stack_alloc: Remove redundant address computation"

This reverts commit 6a1c625f5e760ea97543056671ab760706301324.

Conflicts:
	stack_alloc.inc