Temporarily disable deRPC tests.

Bug: issue 8136
Change-Id: I6f439cd60d7f08df2c192ecdc5c6312e6aca1f50
Workaround JSONTest failure in Firefox 17

For some reason, calling JSONValue.isNull() sometimes returns non-null
even for JSONArray, JSONBoolean, and JSONObject values.  This only
happens in Firefox 17 in web, draft, or nometa test modes, not in dev
mode.

As a workaround, since JSONNull is a singleton class, return null in
JSONNull.isNull() if 'this' doesn't refer to the singleton instance.

Bug: issue 8139
Change-Id: I8c79c5279a122748047b23d068e2eed4ad9fb22f
makes GWT boolean flags togglable

Change-Id: I5eee53b0b50fde31f3e750ad85c3e089a52fcbab
Don't call toString() on plain Java arrays

Error Prone will soon warn about calling toString() on plain Java
arrays, because the return value is rarely useful.  In JsoTest, we
don't actually care about what it returns because the cast to
String[][] should throw an exception anyway, but presumably we want to
make sure the variable doesn't get discarded as dead and the cast
optimized away.

Instead of applying the Error Prone automated refactoring of calling
java.util.Arrays.toString(), we can just call getClass() instead.

Change-Id: I2e90cf1442d126efe8d7ec866204f20c5e4cf3e9
Merge branch 'master' of https://gwt.googlesource.com/gwt into goodow