milestone: improg writes (almost all) of programs stdout to debug file...

... if so configured to do.
Merge branch 'master' into master-newomprog

Conflicts:
	plugins/omprog/omprog.c
omprog bugfix: parameter "forceSingleInstance" is NOT mandatory
omprog: guard program-to-be-executed against CTL-C

This can frequently happen in debug mode, where rsyslog is terminated
by ctl-c. In any case, SIGINT is not meant to control the child process,
so it should be blocked.
document new omprog "output" parameter