* Changed skill_db array to better memory allocation.
* Reduced MAX_SKILL_LEVEL from 100 to 10 (part of Hercules 0f4a50d135), also has changes on skill_get checks for skill level that more than 10.
* Reduced MAX_SKILL from 5020 to 1200 (actually only 1109 skills are used).
* Added macros for checking Homunculus, Guild, Mercenary, & Elemental skill ranges.
* Added skill check & index validation when player logged in and when @reloadskilldb.
* Corrected `enum e_skill_flag` order for SKILL_FLAG_REPLACED_LV_0's sake.
* Merged 'addtoskill' script command just as alias of 'skill' script command.
Summary:
* Decreased memory usage by map-server reduced up to 50 MB.
* Decreased memory for each player because of mmo_charstatus::skill[] only has 1200 array, before is 5020.
* Please use skill_get_index() for accessing sd->status.skill[] or skill_db[], don't reckless use skill_id as array index.
NOTE:
* Please import upgrade_20150131_skillset.sql
Signed-off-by: Cydh Ramdh <house.bad@gmail.com>
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