Fix xfeatures2d dependencies
Neon optimization of cv::sum
Merge pull request #3239 from mshabunin:xfeatures2d_fix
Neon optimization of cv::convertScaleAbs
Merge pull request #3248 from ilya-lavrenov:arm_sum
Adding division operators to `Point_` class.

Performs element-wise division.
Adding element-wise division operators to Point3_ class.
Updating documentation to reflect division operations.
Merge pull request #3250 from ilya-lavrenov:neon_convert_scale_abs
Fixed GStreamer encoding pipeline frame drop for most cases.

For several muxers and encoders GStreamer still drops the last frame.
Merge pull request #3252 from GravityJack:point-division
Fixed compatibility with GStreamer 1.x.
More accurate selection of color space conversion element for GStreamer 1.x
Merge pull request #3253 from asmorkalov:ocv_gstreamer2