Small changes to ap_casecmpstr[n]() for better performances, see:

http://mail-archives.apache.org/mod_mbox/httpd-dev/201511.mbox/%3CCAKQ1sVOU7xmY-_PaQb0et0GXO-NxtTPBsD4ZU_UbtUzWYOUVTg%40mail.gmail.com%3E

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1722194 13f79535-47bb-0310-9956-ffa450edef68