* c-common.c (struct disabled_builtin, disabled_builtins,
	disable_builtin_function, builtin_function_disabled_p): New.
	(builtin_function_2): Check for disabled built-in functions.
	* c-common.h (disable_builtin_function): Declare.
	* c-decl.c (c_decode_option): Handle -fno-builtin-FUNCTION.
	* doc/invoke.texi: Document -fno-builtin-FUNCTION.
	* doc/extend.texi: Mention -fno-builtin-FUNCTION.

testsuite:
	* gcc.dg/no-builtin-1.c: New test.

From-SVN: r47133