GETINDICES  Get index to label list for each label entry

     IND=GETINDICES(LAB)

 INPUT
    LAB    SDLAB object

 OUTPUT
    IND    Vector with index per SDLAB entry

 DESCRIPTION
 GETINDICES returns relative index to label list for each entry.
 A useful shorthand for GETINDICES is unary minus operator -LAB.

 SEE ALSO
 GETNAMES, GETLIST