cpovirk and cgdecker Update to Truth 0.41, and expect a single failure-message format inst…
…ead of the current multiple possibilities.

Also, update the bundled-for-Ant JUnit from JUnit 3-something to JUnit 4.11. This matches the dependency used by the Maven build. It's necessary to avoid the problem "java.lang.ClassNotFoundException: org.junit.ComparisonFailure." Truth was already using that type as of 0.36[*], so I suspect that we were just getting away with the JUnit 3 dependency because of the vagaries of class loading. Presumably, if a test had ever actually failed in a way that should have produced a ComparisonFailure, the current build setup would have produces the same error.

[*] https://github.com/google/truth/blob/release_0_36/core/src/main/java/com/google/common/truth/Platform.java#L24

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Latest commit 12692cb Jun 14, 2018