PR c++/70462 - unnecessary base ctor variant with final.

PR c++/70462 - unnecessary base ctor variant with final.

As pointed out in the PR, we don't need base 'tor variants for a final
class, since it can never be a base.  I tried also dropping complete
variants for abstract classes, but that runs into ABI compatibility problems
with older releases that refer to those symbols.

	* optimize.c (populate_clone_array): Skip base variant if
	CLASSTYPE_FINAL.
	(maybe_clone_body): We don't need an alias if we are only defining
	one clone.

From-SVN: r272669