Fix bug in equal3 for within() checks on strings

We need to return quickly if the arguments are identical and are not numbers, but need to avoid the identical-ness check for numbers so that we can return false in the case of within(1%<m>)(1%<s>, 1%<s>). The previous code had a logic bug where it skipped identical-ness checks on all within() calls, when it should only skip them for within() calls on numbers

Author: BenMusch

src/js/base/runtime.js

@@ -1987,8 +1987,11 @@ function (Namespace, jsnums, codePoint, util, exnStackParser, loader, seedrandom
           }
           curLeft = current.left;
           curRight = current.right;
+          var isIdentical = thisRuntime.ffi.isEqual(identical3(curLeft, curRight))
 
-          if (!fromWithin && thisRuntime.ffi.isEqual(identical3(curLeft, curRight))) {
+          if (!fromWithin && isIdentical) {
+            continue;
+          } else if (isIdentical && !(isNumber(curLeft) || isNumber(curRight)) && !jsnums.isUnitnum(tol)) {
             continue;
           } else if (isNumber(curLeft) && isNumber(curRight)) {
             if (!jsnums.checkUnit(jsnums.getUnit(curLeft), jsnums.getUnit(curRight))) {