Fix build error on el9.
    
    Fixes the following build error on el9:
     ../bltVecMath.c:767:59: error: 'Tcl_Interp' has no member named 'result'
      767 |         Tcl_SetErrorCode(interp, "ARITH", "DOMAIN", interp->result,
          |                                                           ^~
     ../bltVecMath.c:774:66: error: 'Tcl_Interp' has no member named 'result'
      774 |             Tcl_SetErrorCode(interp, "ARITH", "UNDERFLOW", interp->result,
          |                                                                  ^~
     ../bltVecMath.c:780:65: error: 'Tcl_Interp' has no member named 'result'
      780 |             Tcl_SetErrorCode(interp, "ARITH", "OVERFLOW", interp->result,
          |                                                                 ^~
     ../bltVecMath.c:789:60: error: 'Tcl_Interp' has no member named 'result'
      789 |         Tcl_SetErrorCode(interp, "ARITH", "UNKNOWN", interp->result,
          |                                                            ^~
     make: *** [Makefile:308: bltVecMath.o] Error 1
     error: Bad exit status from /var/tmp/rpm-tmp.5C71bb (%build)
    
    Signed-off-by: Damian Wrobel <dwrobel@ertelnet.rybnik.pl>