Small changes to rotatelogs:

- add "-n num" to help text
- clarify in help text, that "program is invoked"
  is the "-p" case
- prevent crash with "-v" (verbose) if no
  "-p prog" is used
- add one space for formatting


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1666415 13f79535-47bb-0310-9956-ffa450edef68