Some small optimization:

   - use 'ap_cstr_casecmpn' instead of 'strncasecmp'
   - use 'apr_table_setn' when parameters are constant
   - avoid some memory allocation if the module can not handle a request

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1816919 13f79535-47bb-0310-9956-ffa450edef68