Core/Calendar: Fix memory leak in CMSG_CALENDAR_ADD_EVENT handler.

Fix memory leak when malformed CMSG_CALENDAR_ADD_EVENT is received.
This properly fixes the memory leak that 51e38872c72e16bb0f09e660c2660759021b2176 tried to fix, reverted in 927f16de49d6cee6562e2d6bc48714572d142c03.
DB/Quest: The Plains of Nasam

By dr-j, closes #3979
DB/SAI: Fix Stone statues

By untaught, closes #1923
DB/Quest: Fix Slim Pickings

By dr-j closes #1900
DB/Quest: The Story Thus Far...

By untaught, closes #11417
DB/Quest: Fix Basic Orders

By untaught, closes #11925
DB/Quest: All Things in Good Time

By dr-j, closes #11441
DB/Quest: Valduran the Stormborn

By w1sht0l1v3, closes #4499
Core/Loot: Fix disenchant exploit

Fix exploit that allowed to disenchant the same item multiple times.
Fixes #12116
DB/Spell: Arcane missiles & Penance critical chance reduction

By gecko32, closes #11949
DB/SAI: Prevent mass spawn of Heb'Jins Bat

By dr-j, closes #11596
DB/Quest: Cocooned

By dr-j, closes #11478
DB/Creature: Fix Proto-drake (23689)

By dr-j, closes #11782
DB/Creature: Enraged Stanley

By dr-j, closes #11774
DB/Quest: Jack Likes His Drink

by dr-j, closes #11453
DB/Creature: Fix Gurgthock

By dr-j, closes #11189
DB/Quest: The Ring of Blood: The Blue Brothers

By dr-j, closes #11185
Merge branch 'master' of https://github.com/TrinityCore/TrinityCore into ghbb
DB/Spells: Added some effects to a couple of serverside spells
DB/Gameobject: Add Cosmetic Explosion Trap spawns

By untaught, updates #12243