final/override were only implemented in g++ 4.7.

include/ChangeLog
2016-10-14  Pedro Alves  <palves@redhat.com>

	* ansidecl.h [__cplusplus >= 201103 && GCC_VERSION < 4007] (FINAL,
	OVERRIDE): Define as empty.
	[__cplusplus < 201103 && GCC_VERSION < 4007] (FINAL): Define as
	__final.
	[__cplusplus < 201103 && GCC_VERSION >= 4007] (OVERRIDE): Define as
	empty.

From-SVN: r241167