Bug fixes and other changes

#Fixed issue where a corrupted map cache would lead to a crash
*Moved Big-endian compatibility functions to common/utils.h
#Fixed issue 8162
*http://hercules.ws/board/tracker/issue-8162-loadnpc-doesnt-trigger-oninit-of-duplicate-npcs/
*Added options to npc_parse_duplicate
#Fixed issue 8169
*http://hercules.ws/board/tracker/issue-8169-script-command-guildskill-skill-idlevel-not-working-as-intended/
*Changed *guildskill behavior, now it behaves exactly as depicted in the documentation
*Updated *guildskill documentation
#Added missing GBI types to mapif_parse_GuildBasicInfoChange now it's possible to change guild exp, lv, skill point and skill information
#GeoIP revamp
*GeoIP module was partially rewritten
*Added several data checks to prevent corruption and crashes
*Updated GeoIP database
*See https://github.com/maxmind/geoip-api-c/blob/master/libGeoIP/GeoIP.c for more information
#Added packetver checks regarding NST_MARKET
*Now *tradertype warns if user is trying to use this feature with older clients