Make Pals only return amount of memory requested

The PAL API previously allowed for returning more memory than asked for.
This was when the PAL performed the alignment work, now this is done in
large alloc, so removing from the PAL.

README.md

@@ -163,9 +163,9 @@ pages, rather than zeroing them synchronously in this call
 
 ```c++
 template<bool committed>
-void* reserve(size_t* size, size_t align);
+void* reserve(size_t size, size_t align);
 template<bool committed>
-void* reserve(const size_t* size) noexcept;
+void* reserve(size_t size) noexcept;
 ```
 Only one of these needs to be implemented, depending on whether the underlying
 system can provide strongly aligned memory regions.