Fix TreeDiffer to work correctly on break statements without labels.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=75037071
Instead of compiling source files to match them against other files, add a parsesWithoutError() chain instead.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=75057050
Merge pull request #55 from google/moe_writing_branch_from_8867a5afd90e3e12c01a964b073fd8558e029aa9

A fix to TreeDiffer, and a different approach to generated sources evaluation.