Largish rework: scan while1stmt for jump out ..

to disambiguate.

For this, we use the self.opc JUMP_OPS sets.
For this, we neeed to store opc in the parse object.

DRY uses of "last = min(last, len(tokens))

uncompyle6/parsers/reducecheck/ifelsestmt.py

@@ -116,7 +116,7 @@ def ifelsestmt(self, lhs, n, rule, ast, tokens, first, last):
             if jf_cf_pop == "jf_cf_pop" and jf_cf_pop[0] == "JUMP_FORWARD":
                 jump_forward = jf_cf_pop[0]
                 endif_target = int(jump_forward.pattr)
-                last_offset = tokens[min(last, n-1)].off2int()
+                last_offset = tokens[last].off2int()
                 if endif_target != last_offset:
                     return True