This patch eliminates the arglocs array I introduced to build_over_call
in r264887, and eliminates the call to maybe_constant_value when building
"fargs" (thus retaining location wrapper nodes).

Instead, this patch requires that any checks within
check_function_arguments that need folded arguments do their own folding.

Of the various checks:
(a) check_function_nonnull already calls fold_for_warn,
(b) check_function_format doesn't need folding
(c) check_function_sentinel needs fold_for_warn in one place, which the
patch adds, and
(d) check_function_restrict needs per-argument folding, which the patch
adds.  Given that it scans before and after resetting TREE_VISITED on
each argument, it seemed best to make a copy of the array, folding each
argument from the outset, rather than repeatedly calling fold_for_warn;

gcc/c-family/ChangeLog:
	PR c++/56856
	* c-common.c (check_function_sentinel): Call fold_for_warn on the
	argument.
	(check_function_restrict): Rename param "argarray" to
	"unfolded_argarray", and make a copy named "argarray", calling
	fold_for_warn on each argument.
	(check_function_arguments): Add note about responsibility for
	folding the arguments.

gcc/cp/ChangeLog:
	PR c++/56856
	* call.c (build_over_call): Eliminate the "arglocs" array, and the
	call to maybe_constant_value when building "fargs".

From-SVN: r265609