Set on_crash = 'preserve' in default Xen config

Without this, if a domain crashes quickly at startup Xen may not be
able to attach to the console fast enough to display the error.
Merge pull request #270 from talex5/on_crash

Set on_crash = 'preserve' in default Xen config
Revert "Do not implicitely manage the installation of OPAM packages with the mirage tool"

We need the dependencies installed to calculate the linker options now.

This reverts commit c5355482a2f4efe473e0eb09fae73be7a8cb4432.
Don't tell the user to run "make depend"

We now do it automatically again.
Don't redirect "opam install" output to log

Installation can take a long time and the user will want to see what is
happening.
Discover and link C stub dependencies in --xen mode
Don't test against OCaml 4.00.1

We no longer support it.
Travis: install missing test package
Merge pull request #265 from talex5/link_c_stubs

Discover and link C stub dependencies in --xen mode
Fix determination of mirage-xen location.

The issue arise when findlib.conf contains multiple paths.  This fix delays
the ocamlfind query to build-time, so that we can query the library directly
rather than trying to pick out the correct top-level library path.
Corrected FLOW doc string

It does not block until the buffers are "successfully transmitted", only
until they are queued to be sent.
Merge pull request #283 from talex5/flow-docs

Corrected FLOW doc string
Generate a .xe shell script which can upload to a xapi host/ XenServer

The script needs:
* the xe binary
* the xe-unikernel-upload binary
* a $HOME/.xe config file

Signed-off-by: David Scott <dave.scott@citrix.com>
chmod name.xe to 0o755

Signed-off-by: David Scott <dave.scott@citrix.com>
Bug fixes in generated .xe shell script

Signed-off-by: David Scott <dave.scott@citrix.com>
xe: make script more robust

  - add 'set -e' to stop on error
  - print the VDI, VM uuid (since the names aren't guaranteed to be unique)

Signed-off-by: David Scott <dave.scott@citrix.com>
xe: store the VIF uuid in a $VAR

  - avoids unnecessarily writing the bare UUID to the console
  - restores symmetry with VBD handling

Signed-off-by: David Scott <dave.scott@citrix.com>
escape quotes (apostrophes)

sorry but this was really bugging me..
Merge pull request #288 from moonlightdrive/patch-1

escape quotes (apostrophes)
Merge pull request #285 from djs55/xe

Generate a name.xe shell script to upload unikernel to a host running xapi (eg XenServer)