Added more public constants to <far/types.h>     - added constants for Vtr::INDEX_INVALID and VALENCE_LIMIT     - added inline equivalent to Vtr::IndexIsValid()
Added more public constants to <far/types.h>
    - added constants for Vtr::INDEX_INVALID and VALENCE_LIMIT
    - added inline equivalent to Vtr::IndexIsValid()

lookup1980/OpenSubdiv,nyotis/OpenSubdiv,xldeveloper/OpenSubdiv,xldeveloper/OpenSubdiv,poljere/OpenSubdiv,takahito-tejima/OpenSubdiv,shengfuintel/OpenSubdiv,shengfuintel/OpenSubdiv,anshuarya/OpenSubdiv,takahito-tejima/OpenSubdiv,c64kernal/OpenSubdiv,nyotis/OpenSubdiv,anshuarya/OpenSubdiv,poljere/OpenSubdiv,c64kernal/OpenSubdiv,c64kernal/OpenSubdiv,xldeveloper/OpenSubdiv,poljere/OpenSubdiv,shengfuintel/OpenSubdiv,anshuarya/OpenSubdiv,lookup1980/OpenSubdiv,nyotis/OpenSubdiv,lookup1980/OpenSubdiv,takahito-tejima/OpenSubdiv