Limit new value calculations to first order effects.

Limit new value calculations to first order effects.

When utilzing poor values during propagation, we mostly care about values that
were undefined/processed directly used in calcualting the SSA_NAME being
processed.  2nd level derivations of such poor values rarely affect the
inital calculation.  Leave them to when they are directly encountered.

	* gimple-range-cache.cc (ranger_cache::ranger_cache): Adjust.
	(ranger_cache::enable_new_values): Set to specified value and
	return the old value.
	(ranger_cache::disable_new_values): Delete.
	(ranger_cache::fill_block_cache): Disable non 1st order derived
	poor values.
	* gimple-range-cache.h (ranger_cache): Adjust prototypes.
	* gimple-range.cc (gimple_ranger::range_of_expr): Adjust.