Don't crash when the arguments keyword is used as an index.

Fixes issue 1157.
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=57672530
[FUZZER] Putting all probabilities in one place and make it object-oriented without dependency injection
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=57673611
[NEW TYPE INFERENCE]

Process externs in GlobalTypeInfo
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=57681797
Automated g4 rollback of changelist 45835331.

*** Reason for rollback ***

rollback unused "RenameVars2" "ShadowVariables2"

*** Original change description ***

Create RenameVars2.

***
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=57690231