improve command-line parsing

example invocations now flagged as invalid:
  specifying UTC offset with size-based rotation
  specifying -l with size-based rotation
  specifying both -l and UTC offset

range checking of integer parameters not attempted; basic data type issues may need
to be addressed first such as the use of unsigned int for max file size


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@596698 13f79535-47bb-0310-9956-ffa450edef68