ofxiOSVideoPlayer getPixels fix.

correct implementation of `const ofPixels &
ofxiOSVideoPlayer::getPixels() const`
Merge pull request #3364 from julapy/ofxiOSVideoPlayer-getPixels-fix

ofxiOSVideoPlayer getPixels fix.
fixes a bug where total vertex count would not be updated when setting vertex attributes.
Merge pull request #3368 from tgfrerer/fix-totalVerts

fix missing vertex count update
ofVbo: fix the way totalVerts is set