Skill Changes:
* Wizard/Warlock Skill
  * Moved Sightrasher (WZ_SIGHTRASHER) requirement to check Sight (SC_SIGHT) is active or not to skill_check_condition_castend section.
  * Fixed Sightrasher (WZ_SIGHTRASHER) splash area to 3x3. (bugreport:9298)
  * Now Comet (WL_COMET) cannot hits Hiding target (The mistake is not at flag 0x10000 in skill_db.txt, the flash should be added by SD_ANIMATION). (bugreport:8909).
  * Now Reading Spell Book (WL_READING_SB) checking the number of available spell books in Spell Book DB first to prevent infinite loop.
* Sage Skill
  * Now Abracadabra (SA_ABRACADABRA) checking the number of available skills in Abra DB first to prevent infinite loop.
  * Reduced MAX_SKILL_ABRA_DB from 350 to 160.
* Shadow Chaser Skill
  * Fixed Chaos Panic (SC_CHAOSPANIC) effect. (bugreport:9321).
* Genetic Skill
  * Now Wall of Thorn (GN_WALLOFTHORN) can be knocked back but not a whole skill group and durability (HP & max hit) for each skill unit.
* Guillotine Cross Skill
  * Now Magic Mushroom (SC_MAGICMUSHROOM) effect checks the number of available skills in Magic Mushroom DB first to prevent infinite loop.
  * Changed 'RemoveFlag' in db/magicmushroom_db.txt value to 1 to remove skill by importing. (bugreport:9322).
* Wanderer/Minstrel Skill
  * Now Randomize Spell (WM_RANDOMIZESPELL) checks the number of available skills in Improvise DB first to prevent infinite loop.
  * Reduced MAX_SKILL_IMPROVISE_DB from 50 to 30.
* Rebellion Skill
  * Cleaned up, added, corrected some (missing) sequences & DB values.
  * Fixed Hammer of God (RL_HAMMER_OF_GOD) splash damage.
  * Fixed Shaterred Strom (RL_S_STORM) push back & force to sit effect (for player, or stun for monsters) (first implementation leftover).
  * Fixed Slug Shot (RL_SLUGSHOT) hitrate-distance penalty (first implementation leftover).
  * Fixed Howling Mine (RL_H_MINE) damage ratios (first implementation leftover).
  * Now Bind Trap (RL_B_TRAP) only can be placed 1 at same time.
  * Fixed Bind Trap (RL_B_TRAP) damage calculation by using Caster's DEX, Target's Current HP, & Skill Level. FIXME: Exact formula still unknown (refers to idAthena formula).
  * Now Dragon Tail (RL_D_TAIL) doesn't split damage among targets anymore.
  * Now Crimson Marker (RL_C_MARKER) will fails to cast if no slot available.
  * Implemented official packet `ZC_C_MARKERINFO` of Crimson Marker (RL_C_MARKER) mini-map marker (first implementation leftover). !TODO: Confirm the packet for older or newer clients (idAthena partial merge r1497)
  * References: http://forums.irowiki.org/showpost.php?p=1387992&postcount=968, follow up 507f047, dd67f9d

Misc:
* Fixed some skills that should work only in shoot range (map_foreachinshootange, by default), and added check for respecting *skill_wall_check* (map_foreachinrange).
* Fixed item stackable check for `/item` command, follow up 9b4d922.
* Fixed npc source file isn't removed properly by @unloadnpcfile. (bugreport:9311).
* Added constantan for status_change_start() and sc_start() scripts as well
  * SCSTART_NONE = 0x0
  * SCSTART_NOAVOID = 0x1
  * SCSTART_NOTICKDEF = 0x2
  * SCSTART_LOADED = 0x4
  * SCSTART_NORATEDEF = 0x8
  * SCSTART_NOICON = 0x10
* Moved and changed itemdb_unique_id() to pc_generate_unique_id().
* Seperated check for skill SC requirement to skill_check_condition_sc_required().
* Added skill unit flag `UF_KNOCKBACK_GROUP`, just an option to make skill unit can be knocked back a whole group.
* Typos and other minor changes!

Signed-off-by: Cydh Ramdh <house.bad@gmail.com>