This should speed up compile times a bit, as well as enable more liberal
use of forward declarations. (Due to SharedPtr not trying to emit the
destructor anymore.)

This is to support the removal of GetHandle soon

Uses less memory (strings and function table is stored in constant data)
and speeds up start up (no need to allocate and copy strings).

Remove unnecessary/unused struct variables.

It was only being used in two places, where it was replaced by a local
constant.

Implemented FSUser::CreateExtSaveData

Withholding my profanity towards Xcode.