* libc/stdio/fflush.c (_fflush_r): Store old errno to check for

	* libc/stdio/fflush.c (_fflush_r): Store old errno to check for
	low-level seek error condition.  Restore old errno in case of
	success.  Don't use new position after seek as error condition,
	rather check for return value of -1 and errno.  Handle EINVAL
	just like ESPIPE.  Only set fp->_offset if errno is 0.