- The "merging" optimization in mod_setenvif did not deal with

- The "merging" optimization in mod_setenvif did not deal with
  SetEnvIfNoCase properly; and it used strcmp() to compare header
  names when it should use strcasecmp().

- Change the merging optimization so that it only considers the most
  recent setenvif for merging.  This means that mod_setenvif will
  consider all directives in the order they appear in the config file.

- Document that mod_setenvif considers directives in the order they
  appear, and give an example use.

- Perform more comparisons at compile-time in order to speed up things
  at compile-time.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@80545 13f79535-47bb-0310-9956-ffa450edef68