libcpp: Enable P1949R7 for C++11 and up as it was a DR [PR100977]

Jonathan mentioned on IRC that:
"Accept P1949R7 (C++ Identifier Syntax using Unicode Standard Annex 31) as
a Defect Report and apply the changes therein to the C++ working paper."
while I've actually implemented it only for -std={gnu,c}++{23,2b}.
As the C++98 rules were significantly different, I'm not trying to change
anything for C++98.

2021-11-30  Jakub Jelinek  <jakub@redhat.com>

	PR c++/100977
	* init.c (lang_defaults): Enable cxx23_identifiers for
	-std={gnu,c}++{11,14,17,20} too.

	* c-c++-common/cpp/ucnid-2011-1-utf8.c: Expect errors in C++.
	* c-c++-common/cpp/ucnid-2011-1.c: Likewise.
	* g++.dg/cpp/ucnid-4-utf8.C: Add missing space to dg-options.
	* g++.dg/cpp23/normalize3.C: Enable for c++11 rather than just c++23.
	* g++.dg/cpp23/normalize4.C: Likewise.
	* g++.dg/cpp23/normalize5.C: Likewise.
	* g++.dg/cpp23/normalize7.C: Expect errors rather than just warnings
	for c++11 and up rather than just c++23.
	* g++.dg/cpp23/ucnid-2-utf8.C: Expect errors even for c++11 .. c++20.