c++: bogus -Wparentheses warning [PR112765]

c++: bogus -Wparentheses warning [PR112765]

We need to consistently look through implicit INDIRECT_REF when
setting/checking for -Wparentheses warning suppression.  In passing
use the recently introduced STRIP_REFERENCE_REF helper some more.

	PR c++/112765

gcc/cp/ChangeLog:

	* pt.cc (tsubst_expr) <case MODOP_EXPR>: Look through implicit
	INDIRECT_REF when propagating -Wparentheses warning suppression.
	* semantics.cc (maybe_warn_unparenthesized_assignment): Replace
	REFERENCE_REF_P handling with STRIP_REFERENCE_REF.
	(finish_parenthesized_expr): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wparentheses-33.C: New test.