Slack bytes in OCCURS are not managed correctly

[efr15]

Describe the bug
When the SYNCHRONIZED clause is used for an item contained in a group which is an OCCURS, some slack bytes might be added by the compiler at the end of each occurrence. Our parser misses them. The length of the group is consequently wrong.

To Reproduce

       IDENTIFICATION DIVISION.
       PROGRAM-ID. TCOCCSLK.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
        01 WORK-RECORD.
           05 WORK-CODE PIC X.
           05 COMP-TABLE OCCURS 10 TIMES.
                10 COMP-TYPE PIC X.
      *       [10 SLACK-BYTES PIC XX. INSERTED BY COMPILER]
                10 COMP-PAY PIC S9(4)V99 COMP SYNC.
                10 COMP-HOURS PIC S9(3) COMP SYNC.
                10 COMP-NAME PIC X(5).
      *        [10 SLACK-BYTES PIC XX. INSERTED BY COMPILER]
           05 VAR-AFTER PIC X.
       PROCEDURE DIVISION.
           GOBACK
           .
       END PROGRAM TCOCCSLK.

Each occurrence of COMP-TABLE has a length = 14 according to our parser:
COMP-TYPE = 1
[SLACK-BYTES = 2]
COMP-PAY = 4
COMP-HOURS = 2
COMP-NAME = 5

Expected behavior
Length should be 16.

[fm-117]

This is tricky as we don't have any data to 'pin' this kind of slack bytes. The slack bytes we currently compute are pinned to the DataDefinition that goes after them but here the slack bytes are related to a whole occurence of an array.

Ideas:

• rework the whole slack bytes system, using fake nodes inserted in the AST at the right position
• check how the property is used, maybe we can get away with this problem by computing the additional slack bytes in PhysicalLength property. It means we would not keep the actual slack bytes count but still account for them in the total length