Merge r1554300, r1554301, r1554994, r1555266 from trunk:

Merge r1554300, r1554301, r1554994, r1555266 from trunk:

core: Support named groups and backreferences within the LocationMatch,
DirectoryMatch, FilesMatch and ProxyMatch directives.

Documentation for the support of named groups and backreferences.

c89 fix

Add a "MATCH_" prefix to variables set within
LocationMatch/DirectoryMatch/FilesMatch.

Submitted by: minfrin, covener, minfrin
Reviewed/backported by: jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1555551 13f79535-47bb-0310-9956-ffa450edef68