* misc/error.c (strerror_r): Do not declare unless [!_LIBC].

* misc/error.c (strerror_r): Do not declare unless [!_LIBC].

	Do not check for HAVE_DECL_STRERROR_R missing unless STRERROR_R_CHAR_P.
	Use strerror_r that is only a macro, even if it is not a function.
	(strerror): Check for HAVE_DECL_STRERROR before declaring.
	(private_strerror): Use prototypes, not old-style function definition.
	(print_errno_message): New function.
	Support the POSIX 'int'-flavored strerror_r, as well as the traditional
	char*-flavored one.
	(error_tail, error, error_at_line): Use it.