Re-order failed tests in steps: after 10, 50 and then every 500

It used to be extremely bad: if the interesting failing test is the last
one (of 300), CEGISLike would test 1000*300 times before ordering it to
make it first.

Now we assume that interesting tests are discovered early.

src/main/scala/leon/synthesis/rules/CEGISLike.scala

@@ -723,7 +723,7 @@ abstract class CEGISLike[T <% Typed](name: String) extends Rule(name) {
 
         var n = 1
         def allInputExamples() = {
-          if (n % 1000 == 0) {
+          if (n == 10 || n == 50 || n % 500 == 0) {
             baseExampleInputs = baseExampleInputs.sortBy(e => -failedTestsStats(e))
           }
           n += 1

src/regression/scala/leon/regression/repair/RepairSuite.scala

@@ -18,7 +18,7 @@ class RepairSuite extends regression.LeonTestSuite {
     "Compiler1.scala"   -> "desugar",
     "Heap4.scala"       -> "merge",
     "ListEasy.scala"    -> "pad",
-    //"List1.scala"       -> "pad",
+    "List1.scala"       -> "pad",
     "Numerical1.scala"  -> "power",
     "MergeSort2.scala"  -> "merge"
   )