Returns message text associated with a given message
    identification code into the caller's buffer. The message can
    be from the system message file or a user-defined message.

    On Alpha and Integrity server systems, this service accepts 64-
    bit addresses.

    Format

      SYS$GETMSG  msgid ,msglen ,bufadr ,[flags] ,[outadr]

    C Prototype

      int sys$getmsg  (unsigned int msgid, unsigned short int

                      *msglen, void *bufadr, unsigned int flags,

                      unsigned char outadr [4]);