Fix an error in the code generator for "repeated" node

[Mingun]

The problem only with repeated expressions with delimiter. We cannot use the same bytecode for the 1st and the others repetitions, because after the first element the saved position is present in the variables stack. The stack in the append loop looks like:

stack: [arr]
stack: [arr element]
stack: [arr+] -- append the first element

Start loop
stack: [arr pos] -- this `pos` shifts all external label indexes in `expression` by 1
stack: [arr pos delimiter]
stack: [arr pos delimiter element]
stack: [arr+] -- append the others elements
Go to start of loop

Fixes #364.