core: Disallow Methods' registration at run time (.htaccess), they may be
used only if registered at init time (httpd.conf).

Calling ap_method_register() in children processes is not the right scope
since it won't be shared for all requests.

Reviewed by: ylavic, covener, icing


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1807754 13f79535-47bb-0310-9956-ffa450edef68