fold-const.c (fold_binary): Use the precision of the type instead of the size of its mode to compute the...

	* fold-const.c (fold_binary) <LT_EXPR>: Use the precision of the
	type instead of the size of its mode to compute the highest and
	lowest possible values.  Still check the size of the mode before
	flipping the signedness of the comparison.

From-SVN: r119422