Substitute an integer for the first occurrence of a marker found
   in the current long error message.

   ERROR

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   marker     I   A substring of the error message to be replaced.
   number     I   The integer to substitute for marker.

   marker     is a character string which marks a position in
              the long error message where a character string
              representing an integer is to be substituted.
              Leading and trailing blanks in marker are not
              significant.

              Case IS significant;  "XX" is considered to be
              a different marker from "xx".

   number     is an integer whose character representation will
              be substituted for the first occurrence of marker
              in the long error message.  This occurrence of the
              substring indicated by marker will be removed, and
              replaced by a character string, with no leading or
              trailing blanks, representing number.

   None.

   None.

   This routine updates the current long error message.  If no marker
   is found, (e.g., in the case that the long error message is
   blank), the routine has no effect.  If multiple instances of the
   marker designated by marker are found, only the first one is
   replaced.

   If the character string resulting from the substitution
   exceeds the maximum length of the long error message, the
   characters on the right are lost.  No error is signalled.

   This routine has no effect if changes to the long message
   are not allowed.

   1.   In this example, the marker is:   #


         The current long error message is:

            "Invalid operation value.  The value was #".


         After the call,


            errint_c ( "#",  5  );

         The long error message becomes:

            "Invalid operation value.  The value was 5".



   2.   In this example, the marker is:   XX


         The current long error message is:

            "Left endpoint exceeded right endpoint.  The left"//
            "endpoint was:  XX.  The right endpoint was:  XX."


         After the call,

            errint_c ( "XX",  5  );

         The long error message becomes:

            "Left endpoint exceeded right endpoint.  The left"//
            "endpoint was:  5.  The right endpoint was:  XX."

   The caller must ensure that the message length, after sub-
   stitution is performed, doesn't exceed LMSGLN characters.

   1) The error SPICE(EMPTYSTRING) is signalled if the input
      string does not contain at least one character, since the
      input string cannot be converted to a Fortran-style string
      in this case.

   2) The error SPICE(NULLPOINTER) is signalled if the input string
      pointer is null.

   None.

   N.J. Bachman    (JPL)

   None.

   -CSPICE Version 1.2.0, 08-FEB-1998 (NJB)

      Re-implemented routine without dynamically allocated, temporary
      strings.  Made various header fixes.

   -CSPICE Version 1.0.0, 25-OCT-1997   (EDW)

   insert integer into error message text