[NEW TYPE INFERENCE] Better checking for nested namespaces.

Collect types of properties of nested namespaces in GlobalTypeInfo.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65628524
[NEW TYPE INFERENCE] Don't crash on unreachable return
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65629681
[NEW TYPE INFERENCE] Don't crash if prop is not declared
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65632116
[NEW TYPE INFERENCE] Don't crash on property access of declared non-objects.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65738071
[NEW TYPE INFERENCE] Warn when we can't infer the type of a @const.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65743852