Java bridge and synthetic methods should not be exported to JS object proxy

[AlexTrotsenko]

On some conditions Java compiler (as well as Kotlin compiler) generates bridge and synthetic methods.

Such methods are needed to provide either backward compatibility (methods with covariant return types are java 1.5+ only) or provide behaviour defined by specification, but not possible with JVM directly (accessing private members of parent class in inner or nested classes).

These methods are not defined in the source code directly and should not be exported to the JS.

[AlexTrotsenko]

@crahda thanks for taking care of PR. I am closing this issue since changes are merged to master.