Clarify an existing requirement of the server_portstr parameter

to ap_proxy_determine_connection(): it must be a buffer of at
least one byte in size.

(And don't bother with using strcpy in order to zap a string.)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1592514 13f79535-47bb-0310-9956-ffa450edef68