Complete the implementation of N4230, Nested namespace definition.

Complete the implementation of N4230, Nested namespace definition.

/c-family
2015-09-21  Ville Voutilainen  <ville.voutilainen@gmail.com>

	Complete the implementation of N4230, Nested namespace definition.
	* c-cppbuiltin.c: Add __cpp_namespace_attributes and
	__cpp_nested_namespace_definitions.

/cp
2015-09-21  Ville Voutilainen  <ville.voutilainen@gmail.com>

	Complete the implementation of N4230, Nested namespace definition.
	* parser.c (cp_parser_namespace_definition): Support namespace
	attributes both before and after the namespace identifier.

/testsuite
2015-09-21  Ville Voutilainen  <ville.voutilainen@gmail.com>

	Complete the implementation of N4230, Nested namespace definition.
	* g++.dg/cpp1y/feat-cxx11-neg.C: Add tests for C++17 namespace
	attributes and nested namespace definitions.
	* g++.dg/cpp1y/feat-cxx98-neg.C: Likewise.
	* g++.dg/cpp1z/feat-cxx1z.C: Likewise.
	* g++.dg/cpp1y/feat-cxx14-neg.C: New.
	* g++.dg/cpp1z/namespace-attribs.C: Likewise.
	* g++.dg/cpp1z/nested-namespace-def1.C: Add tests for attributes
	appearing before the namespace identifier.

From-SVN: r227977