dbc_to_csv: The string-column auto-detector would mark integer fields (e.g.
RaceID=1, SexID=0, BaseSection=0-4) as string columns whenever their small
values were valid string-block offsets that happened to land inside longer
strings. Fix by requiring that an offset point to a string *boundary* (offset
0 or immediately after a null byte) rather than any valid position — this
eliminates false positives from integer fields whose values accidentally alias
path substrings. Affected CSVs (CharSections, ItemDisplayInfo for Classic/TBC)
can now be regenerated correctly.
game_handler: clearDBCCache() is already called by application.cpp before
resetDbcCaches(), but also add it inside resetDbcCaches() as a defensive
measure so that future callers of resetDbcCaches() alone also flush stale
expansion-specific DBC data (CharSections, ItemDisplayInfo, etc.).
