Improve NTSTATUS constant literal generation

[kennykerr]

Much like #2857, NTSTATUS uses the sign bit for severity just like HRESULT does and are traditionally represented in C++ as hex values. Constants are now generated as follows to improve readability and identification:

pub const STATUS_NOT_FOUND: NTSTATUS = 0xC0000225_u32 as _;

Rather than:

pub const STATUS_NOT_FOUND: NTSTATUS = -1073741275i32;

[tim-weis]

Nice, much more comprehensible.

A welcome update, though I'm growing a bit weary of the as _ shorthand. It's easy for a compiler to substitute the _, though a lot harder for a human. Can _ be exchanged for the concrete type (or am I just being overly pedantic here)?

[kennykerr]

Normally, I'd be explicit but these are always directly assigning/initializing an explicit type so it seems overly redundant.