Add files to CLEANFILES for robust make clean.

Add files to CLEANFILES for robust make clean.

At the least, $(BUILT_SOURCES) should be added to CLEANFILES. Also
beneficial is $(api_DATA), and in the case of Java, *.files and *.h.
Also there is a vpp/app/version.h, and some grammar and lex files in
vppapigen.

Change-Id: Ic6d3f2d40ce65e1d9a8b88217fa1f36de393ebb4
Signed-off-by: Burt Silverman <burtms@gmail.com>