[ext] fix the remaining rpa reverse problem

nqp ResizablePMCArray provided its own reverse method, which is now
not needed anymore. We use the better pir method instead.

Also found a syntax problem in parrot_old

Remaining todos:
t/op/lexicals.t                           (Wstat: 256 Tests: 54 Failed: 1)
  Failed test:  27
t/compilers/pge/p5regex/p5rx.t            (Wstat: 0 Tests: 960 Failed: 7)
  Failed tests:  172, 420-421, 442-443, 869-870
t/src/extend_vtable.t                     (Wstat: 512 Tests: 134 Failed: 2)
  Failed tests:  34, 37