kernel-doc: make member highlighting available in all backends

Note that, in order to produce the correct Docbook markup, the "." or "->"
must be separated from the member name in the regex's captured fields.  For
consistency, this change is applied to $type_member and $type_member_func
too, not just to $type_member_xml.

List mode only prints the struct name, to avoid any undesired change in
the operation of docproc.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>