parser.c (cp_parser_decomposition_declaration): Replace decomposition declaration with structured binding in diagnostics.

	* parser.c (cp_parser_decomposition_declaration): Replace
	decomposition declaration with structured binding in diagnostics.
	* decl.c (cp_finish_decomp): Likewise.
	(grokdeclarator): Likewise.

	* g++.dg/cpp1z/decomp1.C: Expect structured binding instead of
	decomposition declaration in diagnostics.
	* g++.dg/cpp1z/decomp2.C: Likewise.
	* g++.dg/cpp1z/decomp3.C: Likewise.
	* g++.dg/cpp1z/decomp4.C: Likewise.
	* g++.dg/cpp1z/decomp5.C: Likewise.
	* g++.dg/cpp1z/decomp6.C: Likewise.
	* g++.dg/cpp1z/decomp7.C: Likewise.
	* g++.dg/cpp1z/decomp8.C: Likewise.
	* g++.dg/cpp1z/decomp13.C: Likewise.
	* g++.dg/cpp1z/decomp14.C: Likewise.
	* g++.dg/cpp1z/decomp18.C: Likewise.
	* g++.dg/cpp1z/decomp19.C: Likewise.
	* g++.dg/cpp1z/decomp22.C: Likewise.
	* g++.dg/cpp1z/decomp23.C: Likewise.
	* g++.dg/cpp1z/decomp24.C: Likewise.
	* g++.dg/cpp1z/decomp25.C: Likewise.
	* g++.dg/cpp1z/decomp26.C: Likewise.
	* g++.dg/cpp1z/decomp28.C: Likewise.

From-SVN: r249948