...by explicitly defaulting the copy/move functions (and, where needed in turn,
also a default ctor) for classes that have a user-declared dtor that does
nothing other than an implicitly-defined one would do, but needs to be user-
declared because it is virtual and potentially serves as a key function to
emit the vtable, or is non-public, etc.; and by removing explicitly user-
provided functions that do the same as their implicitly-defined counterparts,
but may prevent implicitly declared copy functions from being defined as non-
deleted in the future.  (Even if such a user-provided function was declared
non-inline in an include file, the apparently-used implicitly-defined copy
functions are already include, so why bother with non-inline functions.)

Change-Id: I20a2c713f0fea62659d44298c1d98dc9b7f2d5aa
Reviewed-on: https://gerrit.libreoffice.org/58076
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>