Error Prone 2.6.0

Checkers Added:

• CharacterGetNumericValue
• ErroneousThreadPoolConstructorChecker
• FloggerArgumentToString
• FloggerStringConcatenation
• ProtoBuilderReturnValueIgnored
• RethrowReflectiveOperationExceptionAsLinkageError
• SystemOut
• UnnecessaryAnonymousClass

Issues Closed:

• RFE: configurable DoNotCall/RestrictedApi/JdkObsolete/DefaultCharset/JavaTimeDefaultTimeZone check (#1211)
• Add SystemOut checker (#1534)
• WellKnownMutability: add java.awt.Color (#1682)
• IdentityHashMapUsage warnings differ from its documentation (#2095)
• UnusedMethod no longer works (#2215)
• Document naming convention for UnusedMethod (#2223)