Serialization format 23 for nqp-JS

[nwc10]

nqp-JS is currently a cross-compiler, and so needs to be able to read the serialization output of MoarVM. As of Feb 2020, commit 9709537d90d61529 the MoarVM serialization format was bumped from version 22 to version 23, as it now also serializes closure names.

This broke the nqp-JS build, but it seems that no-one noticed.

This fixes the build at 2020-07 (the current release), but unfortunately additional fixes are needed for changes now made on master. (report coming soon)

With this commit atop 2020-07 I still see these test failures:

Test Summary Report
-------------------
t/nqp/060-bigint.t                   (Wstat: 0 Tests: 157 Failed: 2)
  Failed tests:  96-97
t/nqp/100-dispatcher.t               (Wstat: 0 Tests: 16 Failed: 3)
  Failed tests:  6, 10, 14
t/nqp/114-pod-panic.t                (Wstat: 0 Tests: 0 Failed: 0)
  Parse errors: Bad plan.  You planned 1 tests but ran 0.
t/hll/06-sprintf.t                   (Wstat: 0 Tests: 284 Failed: 12)
  Failed tests:  40, 66-76
  Parse errors: Bad plan.  You planned 294 tests but ran 284.
Files=116, Tests=11601, 236 wallclock secs ( 2.54 usr  0.42 sys + 303.40 cusr 21.92 csys = 328.28 CPU)
Result: FAIL

t/nqp/060-bigint.t and t/hll/06-sprintf.t were both also failing in the same way immediately prior to MoarVM commit 9709537d90d61529.

t/nqp/100-dispatcher.t fails new tests added after later by commit aadea88 -- Add nextdispatcherfor/takenextdispatcher ops. Specifically it fails with Trace: NYI: unimplemented QAST::Op nextdispatcherfor and Trace: NYI: unimplemented QAST::Op takenextdispatcher

t/nqp/114-pod-panic.t fails as a result of

commit c4fcc6438d8d6061dcd3ae431d2771f7c58c4c5d
Date:   Fri May 29 20:45:03 2020 +0200

    Fix t/nqp/114-pod-panic with a relocated `nqp` executable

    As `nqp::execname` is an op code not available on JVM and thus resulting
    in a compile time error, a quite dirty workaround is used. We hide the op
    in an eval and retrieve the value via `die`.

    Also there is no sane way to retrieve the current nqp executable name
    available on the JVM, so skip that test there.

 t/nqp/114-pod-panic.t | 49 ++++++++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 21 deletions(-)

It's unclear what the correct fix for that should be - clearly nqp doesn't work totally cleanly as a cross-compiler.

[jnthn]

Looks reasonable to me; will merge it so the PR doesn't bitrot.