Remove libs/jstring as a dependency. It's a dependency of
deps/libx86-ref, so it's been moved in libx86-ref's own repo.
Fix Makefile pointing to the old libx86-ref directory after
moving libx86-ref to another directory.
Move sqlite-helper to its own repo. Since it was a dependency of
libx86-ref, that also moved to its own repo, it's not needed anymore
in this repo.