Address coverity-scan reported issues.

src/sbbs3/atcodes.cpp

src/sbbs3/chat.cpp

src/sbbs3/echocfg.c

src/sbbs3/filedat.c

src/sbbs3/scfglib.h

src/sbbs3/scfglib2.c

src/sbbs3/services.c

src/sbbs3/xtrn_sec.cpp