Added support for apostrophes (') in libconfig's setting names

Special thanks to Ind for pointing me in the right direction and testing
the patch.

Signed-off-by: Haru <haru@dotalux.com>
Changed npcdb_checkid to use MAX_NPC_CLASS2_START and END.
Merge pull request #60 from kisuka/master

Changed npcdb_checkid to use MAX_NPC_CLASS2_START and MAX_NPC_CLASS2_END.