Summary of important user-visible changes for devtools 0.2.0:
-------------------------------------------------------------

 ** `devtools.mcpEval ("Sandbox", true)` runs the evaluating server inside a
    sandbox, on Linux with `bwrap` and `prlimit`.  Read-only inside are the
    system libraries, Octave, the packages named in
    `DEVTOOLS_SANDBOX_PACKAGES` with their dependencies, and the folders named
    in `DEVTOOLS_SANDBOX_FOLDERS`.  There is no shell, no network and none of
    the rest of the home directory, and only an in-memory `/tmp` is writable.
    The server checks the sandbox before answering, refuses to serve if it
    does not hold, and marks every result with
    `_meta["io.github.pr0m1th3as.devtools/sandbox"]`.

 ** In sandbox mode each call runs in a process of its own, killed at the
    deadline together with anything it started, and `/tmp` is emptied before
    the next call.  A call that crashes the interpreter returns an error, and
    the server keeps serving.

 ** A sandbox's memory is limited to the size of the process starting it plus
    2 GB, and its `/tmp` to 2 GB.  `DEVTOOLS_SANDBOX_MEMORY` and
    `DEVTOOLS_SANDBOX_TMP` set other sizes in gigabytes.

 ** `octave_call`, offered in sandbox mode in place of `octave_eval`, calls one
    function by name on typed arguments, spreadsheet ranges included, and
    returns its outputs as typed cells in `structuredContent`.  It is for
    programs such as `octave-calc`.  Ranges of dates and times need the
    datatypes package.

 ** `devtools.selftest` also checks a sandboxed server, where one can run.

 ** The instructions sent to a client no longer run two sentences together.
