c-family: Have -Wformat-diag accept "decl-specifier" [PR103758]

c-family: Have -Wformat-diag accept "decl-specifier" [PR103758]

I'm tired of seeing

cp/parser.c:15923:55: warning: misspelled term 'decl' in format; use 'declaration' instead [-Wformat-diag]
cp/parser.c:15925:57: warning: misspelled term 'decl' in format; use 'declaration' instead [-Wformat-diag]

every time I compile cp/parser.c, which happens...a lot.  I'd like my
compilation to be free of warnings, otherwise I'm going to miss some
important ones.

"decl-specifiers" is a C++ grammar term; it is not actual code, so
should not be wrapped with %< %>.  I hope we can accept it as an exception
in check_tokens.

It was surrounded by %< %> in cp_parser_decl_specifier_seq, so fix that.

In passing, fix a misspelling in missspellings.

	PR c++/103758

gcc/c-family/ChangeLog:

	* c-format.c (check_tokens): Accept "decl-specifier*".

gcc/cp/ChangeLog:

	* parser.c (cp_parser_decl_specifier_seq): Replace %<decl-specifier%>
	with %qD.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/constexpr-condition.C: Adjust dg-error.

(cherry picked from commit bb936163e28fdbe1a751c55d5e5975e036322a3d)