The hot-cold solver previously was unable to perform narrowing if given
a temperature change of "SAME", leading to less-than-optimal results
when a number of otherwise-possible solutions could be removed from the
possible results by inferring that since they would have yielded a
"COLDER" or "WARMER" temperature change. This commit removes possible
solutions which are absolutely closer or farther from the previous
tested location.
One pre-exisitng test needed to be updated to pass with this change, as
it expected results to be narrowed more slowly than they now are. In
addition, a minimal test case with only two starting locations has been
added to demonstrate this change is working correctly.
73d37c061b