ntdll: implement RtlMakeHandleAllocated to mark handles as vailid

[Robert Shearman]

Jeff Latimer wrote:
> This patch automates the marking of a handle as allocated as part of 
> RtlAllocateHandle.  I can't see any reason for not providing a 
> complete function handle as part of allocating it.
>
> Changelog:
> Mark handle as valid as part of RtlAllocateHandle.

 From my vague memory of writing the tests, I don't think Windows does 
this (or I wouldn't have written the code in the tests to make the 
handle valid).

-- 
Rob Shearman