Allow MXBean in IdentifierName

[PhilippWendler]

Naming an interface with the suffix MXBean marks it as being an MXBean. This should be allowed by the IdentifierName check such that one does not have to add a suppression to every MXBean interface.

There is also an @MXBean annotation that can be used as an alternative for the name suffix, but MXBeans are basically always a public API (they can be accessed via the JVM management interface), so probably many users will not want to rename existing types.