Edit WebSubmit Function

This function is used in a "withdraw approval request" submission
in order to register the withdral of the request in the WebSubmit
"Approvals" DB (sbmAPPROVAL).
At the time of the approval request withdrawal, the document could be
in one of several different approval "states" and depending upon that
state, the action taken by this function differs. The states are as
follows:
      * Approval of the document has previously been requested and it is
        still in the "waiting" state.
         -> In this case, the status of the document in the sbmAPPROVAL
            table is set to "withdrawn".
      * Approval for the document has never been requested.
         -> In this case, there is nothing to do.
      * Approval of the document has previously been requested, but the
        document was rejected.
         -> In this case, it's too late to withdraw the approval request
            and there is nothing left to do.
      * Approval of the document has previously been requested and it has
        been approved.
         -> In this case, it's too late to withdraw the approval request
            and there is nothing left to do.
      * Approval of the document has previously been requested, but the
        request withdrawn.
         -> In this case, there is nothing to do.

@param categ_file_withd: (string) - some document types are
       separated into different categories, each of which has its own
       referee(s).
       In such document types, it's necessary to know the document-
       type's category in order to choose the referee.
       This parameter provides a means by which the category information
       can be extracted from a file in the current submission's working
       directory. It should therefore be a filename.

@param categ_rnseek_withd: (string) - some document types are
       separated into different categories, each of which has its own
       referee(s).
       In such document types, it's necessary to know the document-
       type's category in order to choose the referee.
       This parameter provides a means by which the category information
       can be extracted from the document's reference number.
       It is infact a string that will be compiled into a regexp and
       an attempt will be made to match it agains the document's reference
       number starting from the left-most position.
       The only pre-requisite is that the segment in which the category is
       sought should be indicated with .
       Thus, an example might be as follows:
          ATL(-COM)?--.+
       This would allow "PHYS" in the following reference number to be
       recognised as the category:
          ATL-COM-PHYS-2008-001

@return: (string) - a message for the user.

@Exceptions raised: + InvenioWebSubmitFunctionStop when the submission
                      should be halted.
                    + InvenioWebSubmitFunctionError when an unexpected
                      error has been encountered and execution cannot
                      continue.