Merge r1725149, r1726233, r1729374, r1729374 from trunk:

Merge r1725149, r1726233, r1729374, r1729374 from trunk:

allow expressions to be used in SetHandler. Opt-in with expr= prefix.

from feedback, assume all parameters to SetHandler are expressions.

I couldnt come up with a plausible handler name that was an
invalid expression.

1726233 temporarily broke UDS r->handler case sensitivity

1726233 temporarily broke UDS r->handler case sensitivity

Submitted by: covener
Reviewed/backported by: jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1729876 13f79535-47bb-0310-9956-ffa450edef68