Fix times return value, CLK_TCK description

Fix times return value, CLK_TCK description

	[BZ #2636]
	* manual/time.texi (Processor Time): Return type of times is
	elapsed real time since an arbitrary point in the past.
	(CPU Time): Move CLK_TCK from here...
	(Processor Time): ...to here.  Correct description.
	* manual/conf.texi (Constants for Sysconf): Correct description of
	_SC_CLK_TCK.