Fix asserts in opencv

@wallbraker please test and see if this fixes your asserts still - it's your commit, plus a few of my own to deal with stereoCalibrate non-fisheye only wanting f32, and things I saw to fix while doing that.

Calibration of a camera when called "fisheye" is still much slower than when not (tested with ps4 camera in both cases) and I'm not sure why, but kernel reasons meant I didn't get around to profiling today.