The underlying change here was to add the new WebDAV/DeltaV methods

The underlying change here was to add the new WebDAV/DeltaV methods
now that it has an RFC. At the same time, I revamped a good chunk of
the name <-> number mapping code in http_protocol.c

* add M_FOO constants for the new RFC 3253 (DeltaV) methods. label
  where each of the builtin methods comes from.

* moved METHOD_NUMBER_FIRST/LAST from http_protocol.h into
  http_protocol.c since they weren't used anywhere else and they
  weren't namespace-protected.

* create register_one_method() and use it to insert all builtin
  methods (at _init() time) and extended methods into the registry.

* add a lookup_builtin_method() to quickly map a method name to a
  builtin method number.

* rebuild ap_method_number_of() to use the new lookup function.

* revamp ap_method_name_of() to use the registry to locate the name
  for any method number. add a pool argument (no callers in the core
  code needed to be updated)

* revamp make_allow() to deal with the new method numbers and all
  extended methods.

* in mod_dav, use the new method numbers rather than registering the
  DeltaV methods.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94015 13f79535-47bb-0310-9956-ffa450edef68