Make TestCase methods protected that should have been protected all along

[sebastianbergmann]

• any() (should also not be static)
• never() (should also not be static)
• atLeast() (should also not be static)
• atLeastOnce() (should also not be static)
• once() (should also not be static)
• exactly() (should also not be static)
• atMost() (should also not be static)
• returnValue() (should also not be static)
• returnValueMap() (should also not be static)
• returnArgument() (should also not be static)
• returnCallback() (should also not be static)
• returnSelf() (should also not be static)
• throwException() (should also not be static)
• onConsecutiveCalls() (should also not be static)
• getActualOutputForAssertion()
• expectOutputRegex()
• expectOutputString()
• expectException()
• expectExceptionCode()
• expectExceptionMessage()
• expectExceptionMessageMatches()
• expectExceptionObject()
• expectNotToPerformAssertions()
• getMockBuilder()