matlab_cp2tform small error in equation

[chandraOloid]

hi @clcarwin
Thank you for this awesome torch impl of sphface

quickly jumping into the code in file matlab_cp2tform

Line 407-408 (in python this is copy by reference for arrays, so xy is now changed when you change xyR)

 xyR = xy
 xyR[:, 0] = -1 * xyR[:, 0]

Line 143-144 (in matlab this is copy by value for mats, so xy is not changed when you change xyR)

xyR = xy;
xyR(:,1) = -1*xyR(:,1);

Very likely this should be on line 407

import copy
xyR = copy.deepcopy(xy)