c++: Avoid informs without a warning [PR109278]

c++: Avoid informs without a warning [PR109278]

On the following testcase we emit notes in
maybe_inform_about_fndecl_for_bogus_argument_init
despite no warning/error being printed before it.
This is for the extended floating point type conversions where pedwarn
is used, and complained is used there for 2 different purposes,
one is whether an unspecific error should be emitted if we haven't
complained otherwise, and one whether
maybe_inform_about_fndecl_for_bogus_argument_init should be called.
For the 2 pedwarns, currently it sets complained to true regardless of
whether pedwarn succeeded, which results in the undesirable notes printed
with -w.  If complained is initialized to result of pedwarn, we would
emit an error later on.

So, the following patch makes complained a tristate, the additional
error isn't printed if complained != 0, and
maybe_inform_about_fndecl_for_bogus_argument_init is called only if
complained == 1, so if pedwarn returns false, we can use complained = -1
to tell later code not to emit an error and not to call
maybe_inform_about_fndecl_for_bogus_argument_init.

2023-03-30  Jakub Jelinek  <jakub@redhat.com>

	PR c++/109278
	* call.cc (convert_like_internal): If pedwarn for extended float
	type conversions doesn't report anything, avoid calling
	maybe_inform_about_fndecl_for_bogus_argument_init.

	* g++.dg/cpp23/ext-floating15.C: New test.