[TW]Core/MeleeSpellHitResult: Shred & backstab

Fix error in commit 928c37e697b6a516f7d9eb2479503fd188f04885
also just return SPELL_MISS_NONE no need to go through below checks
[TW] Core/Spell: Primal Fury fix idea

- Maybe path to solution seems to work but is somewhat hard to test.
- Bug seems to come from players having both ranks of the talent within
the spell list and then remove or adding rank breaks primal fury(maybe).
Core/Arena: PR/MMR rating change on leave

- Fixes issue if player was last participant in arena match and left
they would avoid rating loss
Merge pull request #32 from gecko32/TWpatch2

[TW]Core/MeleeSpellHitResult: Shred & backstab
Merge pull request #34 from gecko32/ArenaPatch

Core/Arena: PR/MMR rating change on leave
Merge branch 'master' of https://github.com/TrueWoW/TrinityCore