Mockups with "$advice" fail when target class has private methods

[jmf-tls]

• Version of JMockit that was used:
  1.49 (also in master branch at 5c6a2df)

• Description of the problem or enhancement request:

According to the documentation for the "$advice" method,

If defined, this fake method will handle executions of each and every method in the target class (or classes, when applying the fake over unspecified classes from a base type).

However, if the target class contains a private method, the tests fail when creating a new mock, with an IllegalArgumentException ("Unsupported fake for private method.....").
I created a pull request that adds a validation for this issue on the FakingEverythingTest: #702

In this case, I think private methods should either be supported or ignored.