071e23fe "add move operators for VclPtr" added
(among other things) a move assignment operator that rather copied m_rInnerRef.
But if b72c6feb "manage VCL widgets using
rtl::Reference" had not pointlessly introduced a user-declared copy constructor
in the first place, all the copy/move special member functions would be
implicitly declared (as VclPtr does not have a user-declared destructor).

Change-Id: I1bec05a7a1b5b48a7b7d74e64a88f118454f8cb2
(cherry picked from commit deaeae4d)
Reviewed-on: https://gerrit.libreoffice.org/31682Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>