added failonerror and fork to build files and a small fix for the javagenerator

I observed strange behaviour when running the examples on a machine with custom ant deploy.
Basically the problem was related to the fact that if fork is not used for the java tasks, it would inherit the classpath used by ant, thus the SbeTool and OtfExample failed.

Also, I have regenerated the otf decoder stubs because of some checkstyle warnings.