Closure Conversion - failing impala tests

[leissa]

There are a couple of failing impala test cases:

• Remove --clos flag from impala again
• Remove --clos flag for impala in test script
• Fix non-closure related test cases that fail if clos plugin is loaded
• Fix codegen/cconv/typed_cc/recursion.impala
• Fix codegen/cconv/typed_cc/closure_rec.impala

[leissa]

One of the problems was that the SSAConstr sometimes introduces new vars behind the return continuation.