A few more updates to the Porting Guide:     - added a brief subsection dealing with changes for Face Varying     - added a subsection on ordering of refined vertices and faces
A few more updates to the Porting Guide:
    - added a brief subsection dealing with changes for Face Varying
    - added a subsection on ordering of refined vertices and faces

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