Compiler warnings - yuck!

Moved ap_proxy_string_read() to proxy_util.c so it can be used by
proxy_http.c
PR:
Obtained from:
Reviewed by:


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@88777 13f79535-47bb-0310-9956-ffa450edef68