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/README

@@ -1,8 +1,11 @@
 Files in this directory contain very simnple constructs that work
 across all versions of Python.
 
-Their simnplicity is to try to make it easier to debug grammar
-and AST walking routines.
+Their simplicity is to try to make it easier to debug scanner, grammar
+and semantic-action routines.
+
+We also try to make the code here runnable by Python and when run should
+not produce an error.
 
 The numbers in the filenames are to assist running the programs from
 the simplest to more complex. For example, many tests have assignment

test/simple_source/exception/20_try_except.py

@@ -0,0 +1,5 @@
+for i in (1,2):
+    try:
+        x = 1
+    except ValueError:
+        y = 2

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