Enable experimental sbbsexec modes (e.g. redir DOS I/O)

Added undocumented experimental options -I and -O to enable DOS input and output interception modes in sbbsexec (e.g. to be used possibly with '-h'). Also -M to specify sbbsexec mode value by number (e.g. 3 to enable DOS Input/Output redir).

Added '-n' option to specify node number (probably no real value/need).

Safe string formatting.
14 jobs for dailybuild_linux-x64 in 9 minutes and 47 seconds (queued for 15 seconds)
Status Name Job ID Coverage
  Build
passed jsdoor-freebsd #35683
FreeBSD

00:03:48

passed jsdoor-linux #35684
Linux

00:06:44

passed jsdoor-windows #35686
FreeBSD

00:01:54

passed sbbs-freebsd #35678
FreeBSD

00:05:20

passed sbbs-linux #35673
Linux

00:09:35

passed sbbs-windows #35676
Windows

00:05:00

passed sexpots-freebsd #35685
FreeBSD

00:00:11

passed sexpots-linux #35674
Linux

00:00:15

passed sexpots-windows #35677
Windows

00:00:22

passed syncdraw-freebsd #35681
FreeBSD

00:00:22

passed syncdraw-linux #35682
Linux

00:01:00

passed syncterm-freebsd #35679
FreeBSD

00:00:58

passed syncterm-linux #35675
Linux

00:02:41

passed syncterm-windows #35680
FreeBSD

00:01:44