Log Message:
- mention conflict with others version (news/slrn, wip/slrn-pl)
- upgrade latest snapshot, changes from -11 to -15:
 
 12. src/nntplib.h: Removed duplicate declarations of nntp_server_cmd
     and nntp_server_vcmd. (Li Hong).
 13. src/decode.c: If an output file already exists, create a new one
     by appending an integer to the name.
 14. src/slrn.c: work around a SLang_getkey bug that arises when the
     underlying read system call is interrupted, and the interrupt hook
     creates a different read descriptor.
 15. src/misc.c: All error messages (including slang tracebacks) are
     logged to the --debug output file.