PR c++/98646 - spurious -Wnonnull calling a member on the result of static_cast

PR c++/98646 - spurious -Wnonnull calling a member on the result of static_cast

gcc/c-family/ChangeLog:

	PR c++/98646
	* c-common.c (check_nonnull_arg): Adjust warning text.

gcc/cp/ChangeLog:

	PR c++/98646
	* cvt.c (cp_fold_convert): Propagate TREE_NO_WARNING.

gcc/ChangeLog:

	PR c++/98646
	* tree-ssa-ccp.c (pass_post_ipa_warn::execute): Adjust warning text.

gcc/testsuite/ChangeLog:

	PR c++/98646
	* g++.dg/warn/Wnonnull5.C: Adjust text of an expected warning.
	* g++.dg/warn/Wnonnull10.C: New test.
	* g++.dg/warn/Wnonnull9.C: New test.