[BUG] Add support for the kotlin incremental compiler

[rzwitserloot]

Describe the bug
The annotationprocessor entrypoint checks the actual runtime type of the ProcessingEnv and will immediately abort on modern versions of kotlinc, which is relevant as it's the default choice for the most recent android dev kit. The actual type of the processingEnv is:

https://github.com/JetBrains/kotlin/blob/master/plugins/kapt3/kapt3-base/src/org/jetbrains/kotlin/kapt3/base/incremental/incrementalProcessors.kt#L75

which is just a wrapper around the usual javac one probably (that class is a wrapper, I haven't yet investigated what it wraps, but presumably, standard javac), overriding only the filer, and the source of the filer is in that link as well. Shouldn't be too difficult to adjust the bits of lombok that need access to the AST to 'unwrap' the wrapper.

See also: https://groups.google.com/forum/#!topic/project-lombok/xwnsiaRK3fM

[rzwitserloot]

I'm at this point not sure if the above problem description (that is: That we need to add a type of processingEnv) is still relevant, given that the lombok plugin for kotlinc exists. I'm closing this as duplicate of #1169.