Added libotr back to configure by default

Renamed to BUILD_OTR3
Use AC_SEARCH_LIBS for otr
Check for libotr version
Added otr4.c
Added libotr4 message handlers
Changed functions for libotr4 compatibility
Merge branch 'master' into libotr4
Merge branch 'libotr4' of github.com:boothj5/profanity into libotr4
Changed OTR policy for otr4.c
Allow V3, use OTRL_INSTAG_BEST, output error event when no message
Use instag master, and skip fragmentation
Added command to show libotr version