Int 68 Fn 04  - Appc/pc - Transaction Processing                           [N]

   AH = 04h
   DS:DX -> control block (see #3373)

Return: control block updated

Format of APPC/PC control block:
Offset Size    Description (Table 3373)
 00h 12 BYTEs  reserved
 0Ch   WORD    verb (action)
       2500h TP_ENDED
       2900h TP_VALID
 0Eh  6 BYTEs  00h
 14h   DWORD   (big-endian) return code (see #3339)
 18h   WORD    00h
 1Ah  8 BYTEs  (big-endian) TP_ID
 22h   DWORD   -> CREATE_TP record (only if verb = 2900h)