ocaml: Break circular dependency of mlguestfs.cma{,x} <-> guestfs.cm{o,x}
ocaml: Fix and enable parallel builds.

We only have to serialize the two calls to ocamlmklib, since both will
try to create a file called 'libmlguestfs.a'.  Apart from that,
parallel builds here should be fine.
ocaml tools: Enable parallel builds.

In particular, building virt-sysprep is slow because there are so many
modules.  Enable parallel builds.  If it breaks, we should fix it, not
work around it.
java: Enable parallel builds.

This reverts commit 89404ec0ba9781b55cb3a87689bcc519e7d73ea2.
java: Format CLEANFILES rule.