Constrain lbfgs to OCaml < 4.02.0.

lbfgs doesn't build on OCaml 4.02.*:

```
File "src/lbfgs.mli", line 109, characters 24-26:
Error: String literal begins here
Command exited with code 2.
``
Add mirage-console.2.1.0

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Add xentropyd.0.9.1

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Add xe.0.6.3

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
xentropy depends on ocaml 4.01.0+ for |>

Signed-off-by: David Scott <dave.scott@citrix.com>
xe.0.6.3 depends on oasis (in the Makefile)

Signed-off-by: David Scott <dave.scott@citrix.com>
containers 0.7.0.1 (missing flags)
xentropyd.0.9.1: improve docs (and retrigger travis)

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #3262 from yallop/lbfgs-constraint

Constrain lbfgs to OCaml < 4.02.0.
Merge pull request #3268 from djs55/mirage-console.2.1.0

Add mirage-console.2.1.0
Merge pull request #3271 from c-cube/containers.0.7.0.1

containers 0.7.0.1 (missing flags)
Merge pull request #3270 from djs55/xe.0.6.3

Add xe.0.6.3
Merge pull request #3269 from djs55/xentropyd.0.9.1

Add xentropyd.0.9.1
froc requires ocaml < 4.02.0 to build
ancient.0.9.0 requires ocaml <4.03.0
cryptokit requires ocaml <4.03.0 to compile

Due to removed uint32 typedef:

```
src/stubs-md5.c:21:9: error: unknown type name 'uint32'
  uint32 buf[4];
  ^
```
Merge pull request #3273 from avsm/ancient-ov

ancient.0.9.0 requires ocaml <4.03.0
Merge pull request #3272 from avsm/froc-ov

froc requires ocaml < 4.02.0 to build
Ctypes 0.3.4.
Merge pull request #3275 from yallop/ctypes-0.3.4

Ctypes 0.3.4.