Merged OCaml front-end

There is now an (optional) OCaml front-end. It can run apps and handle
tab-completion without needing to run any Python, and is therefore much
faster. To install, use "make ocaml && sudo make install".
Log exec() calls
Fixed name reported by --help when using the OCaml front-end
Release 2.3
Start development series 2.3-post
Avoid functions only available in OCaml 4

Debian/unstable is still on OCaml 3.
Added TYPE and DEBUG options to build

Debian wants bytecode binaries with no debug symbols.
Handle ambiguous options in the OCaml

e.g. -r can be --root-uri or --refresh.
OCaml completion for "0install config"
Comments and code tidying