* builtin-types.def (BT_FN_VOID_PTR_VAR): New.
	* builtins.def (BUILT_IN_PREFETCH): Change arguments.
	* builtins.c (expand_builtin_prefetch): Two arguments are now optional,
	with defaults for read prefetch with high degree of locality.
	* doc/extend.texi (__builtin_prefetch): Update documentation.
	* doc/md.texi (prefetch): Add documentation.

From-SVN: r47741