Merge r1667707, r1824332 from trunk:

* mod_proxy: Allow setting options to globally defined balancer from
  ProxyPass used in VirtualHost. Balancers are now merged using the new
  merge_balancers method which merges the balancers options.


mod_proxy: follow up to r1667707: MMN minor bump.


Submitted by: jkaluza, ylavic
Reviewed by: icing, jim, ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1824333 13f79535-47bb-0310-9956-ffa450edef68