* texinfo.tex: Rewrite of index stuff to do better column breaking

	* texinfo.tex: Rewrite of index stuff to do better column breaking
	and balancing.
	The old code failed miserably when the index was just the wrong size,
	e.g., the Autoconf manual with @afourpaper.
	Bug report from: Wilhelm Mueller <muewi@hb.senbvs43.uni-bremen.de>
	Date: Fri, 12 Jun 1998 16:34:49 +0200 (MET DST)
	(\initial): Add more glue around the initial, and make it a
		multiple of \baselineskip.
	(\entry): Add glue before each entry so the columns can always be the
	 same height.
	(\doublecolumnout): Available space no longer needs to handle
	 \partialpage specially.
	(\pagesofar): Take \ht\partialpage into account with \vsize.
	(\enddoublecolumns): Reset \output to avoid calling
		\balancecolumns twice
	(\balancecolumns): Format for readability.
	(\initialskipamount): No longer needed, remove.

	(\hbadness): Increase a bit, boxes that are a little underfull look ok.