Support for autoboxing

- Updated to 4.2 version of ASM.
- Preliminary support for autoboxing.

I encountered a weird NPE from type.getInternalName() while using primitives so my initial reaction was to raise the version to 4.2 which of course did not fix the issue. Further digging around revealed that autoboxing requires bytecode level support and that GeneratorAdapter will be a way around the bug(?)

There is a GeneratorAdapter (at least in 4.2 version) that has unbox/box methods for autoboxing implementation. I replaced couple of lines at SyntheticMethod to get the new tests working and my own use case resolved but I assume that a more robust solution would be needed.