autorotate in-memory jpegs (#8492)

* autorotate in-memory jpegs

* correct indentation (4 spaces)

* imgcodecs: don't apply EXIF rotation for unloaded images

* videoio: don't try to rotate MJPEG stream

* imgcodecs: ByteStreamBuffer::seekoff support all seek "dir"

* imgcodecs: fix condition: "off == egptr() - eback()" is valid offset

Add method KeypointBasedMotionEstimator::estimate(InputArray, InputArray) to support both cpu & opencl algorithm processing

the orignal estimate function has input parameters defined as "Mat", this prevent users to call into algorithm opencl path

Check file name only:
    Excluding from source files list (optimization is disabled):
    C:/Code/SrcExt/OpenCV/Buildv3.2_x64/modules/core/opencl_kernels_core.cpp

The method does cvCheckPixelBackgroundNP (which reads bgmodel)
before it is ever updated (in cvUpdatePixelBackgroundNP). This
initialization is thus needed to avoid reads of unitialized values.

New p3p algorithm (accepted by CVPR 2017) (#8301)

* add p3p source code

* indent 4

* update publication info

* fix filename

* interface done

* plug in done, test needed

* debugging

* for test

* a working version

* clean p3p code

* test

* test

* fix warning, blank line

* apply patch from @catree

* add reference info

* namespace, indent 4

* static solveQuartic

* put small functions to anonymous namespace

Same as https://github.com/opencv/opencv/pull/8525/commits/9210cefb36868e201f7e0c8b84e4ee4f91b5432b but for this file too.