Create data/events*.log file for all platforms and monitoring modes

Previously, data/events*.log was only created by sbbsctrl-Win32

The file is referred to as "events*.log" because if the first terminal server
node number is > 1, then that first node number will be prepended to the
base filename. Also, rolled-over logs and renamed to *.0.log, *.1.log, etc.
up to the configured maximum before being deleted.

This change eliminates the repeated log line dedupe feature for that file
(e.g. the "[x2]" indicator). Also, the "Log Eventsto Disk" option is now
removed from the sbbsctrl->Terminal Server->Configure dialog.

Also, fopenlog() now opens log files non-locked (deny-none), so that the
files can be viewed (e.g. with 'grep' or 'tail -f') while they're open and
being written to. There isn't a concurrent write problem for events*.log
but there may be for other log file openes by fopenlog() - so that should
be investigated.

... for Codefenix's mod that'll parse events*.log for QWKnet statistics.