In some application environments, the mod_dav hook structures are

In some application environments, the mod_dav hook structures are
allocated dynamically. The structures need a context pointer to
represent that dynamic "object", so a pointer was added to the end of
each of the more important structures.

While providers don't need to add this field to their structures (it
will default to NULL), I went ahead and added it to mod_dav_fs for
clarity.

No MMN bump is required because Apache does not use/examine the
fields (only the provider will set and use them).

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@96195 13f79535-47bb-0310-9956-ffa450edef68