Tweak apr_getopt() and its use in ab to avoid compiler warnings.

(Note: apr_initopt() and/or its callers still need tweaking.)
Submitted by:	Bill Rowe
Reviewed by:	Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86045 13f79535-47bb-0310-9956-ffa450edef68