Core/Spells: Correct a check in IsLootCrafting, allows Prismatic Black Diamond to be fixed (a very peculiar spell...)

The following conversation led to this fix: http://paste2.org/p/2816385 (for reference)
DB/Loot: Fix Prismatic Black Diamond
Core/Players: Prevent trading, taking gold from mail and withdrawing from guild bank if it would put the player over gold cap.

Closes #4015
Core/Misc: Fixed a few warning found by static analysis tools.
Merge pull request #2 from TrinityCore/master

Merge