Bug in for loop with try. Add more of 2.7's COME_FROM statements.

spark.py: add tracing reduce rules. main: reduce cutsines.
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test/simple_source/looping/10_for.py

@@ -1,5 +1,8 @@
 # Tests:
 #  forstmt ::= SETUP_LOOP expr _for designator
 #              for_block POP_BLOCK COME_FROM
-for a in b:
-    c = d
+for a in [1]:
+    c = 2
+
+for a in range(2):
+    c = 2