TypelibBuild: add demo-function to print the comment for decls

clang "only" extracts actual doxygen comments as "Comments".

together with test-comment in "arrays.h". to test add the
"printCommentForDecl()" somewhere and call the tool like:

    ./build/tools/typelib-clang-tlb-importer/typelib-clang-tlb-importer -tlbSavePath=save.tlb tools/typelib-clang-tlb-importer/test/arrays.h -- -x c++

note that the comments are not printed yet.

Signed-off-by: Martin Zenzes <martin.zenzes@dfki.de>