Added /stat+ commands support for 2013-12+ clients

- Fixes /str+, /agi+ and the likes, only being able to increase stats by
  1 point on 2013-12 and newer clients.
- As a bonus, on those clients, processing of the /stat+ commands will
  be much faster, and the requested points will be added instantly and
  all at once rather than one at a time like in older clients.

Signed-off-by: Haru <haru@dotalux.com>
Updated HPMHookGen with a HPMDataCheck generator

- It will be used by an upcoming commit by Ind.
- Added dummy HPMDataCheck.h, to test the API bot's capability to
  re-generate it.
- Improved XML parser performance.

Signed-off-by: Haru <haru@dotalux.com>