Fixes #2451 with addition to boilerplate loader

[Dunbaratu]

Fixes #2451

The solution is explained in the comment in the code.

When RUN ONCE skipped the actual program call, it wasn't
cleaning out the args and KOSArgMarker the program call was
supposed to be popping. When you use RUN ONCE with a program
that takes no args, that's not horrible, as it just
left one extra KOSArgMarker on the stack which was fine
but slightly wasted stack space if you do RUN ONCE a lot.
But when you use RUN ONCE interleaved with calls to other
programs that DO expect arguments, and start putting the
PARAMETER statement AFTER the RUN ONCE's, then the fact
that this extra KOSArgMarker was there caused misalignment
of the stack.

My solution was that in the clause where RUN ONCE choses to
skip the program call, have the @lr boilerplate program do
the same thing to the stack that a call would have done, that
is have it pop everything down to an including the topmost
KOSArgMarker. I did that by coding a small kRISC loop there:
like so:

// Keep popping till next thing is argbottom, then pop that too:
pop           <---.
testargbottom     |
br.true ---.      |
jump ------+------'
pop   <----'