c++: failure to suppress -Wsizeof-array-div in template [PR114983]

c++: failure to suppress -Wsizeof-array-div in template [PR114983]

-Wsizeof-array-div offers a way to suppress the warning by wrapping
the second operand of the division in parens:

  sizeof (samplesBuffer) / (sizeof(unsigned char))

but this doesn't work in a template, because we fail to propagate
the suppression bits.  Do it, then.

The finish_parenthesized_expr hunk is not needed because suppress_warning
isn't very fine-grained.  But I think it makes sense to be explicit and
not rely on OPT_Wparentheses also suppressing OPT_Wsizeof_array_div.

	PR c++/114983

gcc/cp/ChangeLog:

	* pt.cc (tsubst_expr) <case SIZEOF_EXPR>: Use copy_warning.
	* semantics.cc (finish_parenthesized_expr): Also suppress
	-Wsizeof-array-div.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wsizeof-array-div3.C: New test.