Merge r1154940 from trunk:

document implicit limitation in AllowOverride Option=Foo -- this doesn't let you
"lock in" any value since the non +/- syntax can zap whatever it wants.




git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1154942 13f79535-47bb-0310-9956-ffa450edef68