avoid mex files in the ni2/private directory

[robertoostenveld]

I am getting this error

Invalid MEX-file '/Users/roboos/Documents/werk/teaching/cns/2122-neuroimaging2/brightspace/ni2/private/ltrisect.mexmaci64':
dlopen(/Users/roboos/Documents/werk/teaching/cns/2122-neuroimaging2/brightspace/ni2/private/ltrisect.mexmaci64, 0x0006): Library not loaded: @loader_path/libmex.dylib
  Referenced from: /Users/roboos/Documents/werk/teaching/cns/2122-neuroimaging2/brightspace/ni2/private/ltrisect.mexmaci64
  Reason: tried: '/Users/roboos/Documents/werk/teaching/cns/2122-neuroimaging2/brightspace/ni2/private/libmex.dylib' (no such file), '/usr/local/lib/libmex.dylib' (no such file), '/usr/lib/libmex.dylib' (no such
  file)
Error in intersect_plane (line 43)
    cnt1(i,:) = ltrisect(v1, v2, v3, l1, l2);
Error in ni2_sensors (line 38)
    [x, y, z, chanpos, tri] = intersect_plane(chanpos, tri, [0 0 0], [1 0 0], [0 1 0]); 

It should not be needed to have mex files in the "ni2" package.