Remove unnecessary global declarations of optional function
implementations:

* modules/ssl/mod_ssl.c (ssl_proxy_enable, ssl_engine_disable): Mark
  static.

* modules/ssl/ssl_private.h (ssl_proxy_enable, ssl_engine_disable):
  Remove declarations.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1487775 13f79535-47bb-0310-9956-ffa450edef68