Teach gen_header to wrap long lines
Regen neubot.h with wrapped lines

No functional change. No API change. No ABI change.
Teach gen_py to wrap long lines
Regen libneubot.py with wrapped lines

No functional change. No API change. No ABI change.
Add gen_java: generate the JNI class with native static methods
configure: also generate LibNeubot.java
Add LibNeubot.java: the file generated by gen_java
Makefile.in: add rule to generate LibNeubot.h
Add to LibNeubot.java implementation comments (via gen_java)