src/method-proto.lisp: Collect arguments in vanilla delegation trampolines.

src/method-proto.lisp: Collect arguments in vanilla delegation trampolines.

In the keyword-arguments overhaul, somehow the case in `make-trampoline'
for trivially `augmenting' the argument list for a vanilla message, as
opposed to hairy varargs or keyword messages, got lost, with the result
that they ended up with no arguments at all.  Needless to say, the C
compiler is unhappy about this.