Enable SetEnvIf to handle taking a regex on the header name (SPECIAL_NOT case).

For example:

SetEnvIf ^TS* ^[a-z].*  HAVE_TS

will cause HAVE_TS to be set if a header beginning with TS appears in the request
and the value of that header starts with [a-z]


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@89325 13f79535-47bb-0310-9956-ffa450edef68