Fixed the eval-real test

So that it passes provided the answer is right to within one part in a million. Also worked on a solution to returning exceptions from make_stack_frame

unit-tests/eval-real.sh

@@ -8,10 +8,15 @@ actual=`echo "(eval 5.05)" |\
   head -2 |\
   tail -1`
 
-if [ "${expected}" = "${actual}" ]
+outcome=`echo "sqrt((${expected} - ${actual})^2) < 0.0000001" | bc`
+
+
+if [ "${outcome}" = "1" ]
 then
     echo "OK"
 else
     echo "Fail: expected '${expected}', got '${actual}'"
     exit 1
 fi
+
+