added compute function to Feature2D (dirty workaround for #2699)
Fix for spurious assert in cv::compareHist

When comparing histograms that look like multi-channel images (e.g a 3D histogram, of 4x4x4 bins, might appear as a CV_32FC4 matrix), cv::compareHist would complain because it was expecting the matrix type() == CV_32F. Now we test matrix depth() == CV_32F instead.
libd1394 2.x support for mingw on windows added
libd1394 2.x support for mingw on windows added
Merge branch 'mingw-libdc1394-2-windows' of https://github.com/dominikrose/opencv into mingw-libdc1394-2-windows
Merge branch 'mingw-libdc1394-2-windows' of https://github.com/dominikrose/opencv into mingw-libdc1394-2-windows
Merge branch 'mingw-libdc1394-2-windows' of https://github.com/dominikrose/opencv into mingw-libdc1394-2-windows
Merge branch 'mingw-libdc1394-2-windows' of https://github.com/dominikrose/opencv into mingw-libdc1394-2-windows
Merge branch 'mingw-libdc1394-2-windows' of https://github.com/dominikrose/opencv into mingw-libdc1394-2-windows
libdc1394 - removed validation for msvc compiler in CMakeLists.txt
Take account of multi-channel matrices when comparing histograms

Ensure that all channels are considered when comparing multi-channel histograms
Bug #2967, basic_structures.rst, fix 2 typos
Bug #2967, void DescriptorMatcher::radiusMatch() // description unclear,
only file:  common_interfaces_of_descriptor_matchers.rst
Bug #2966, insert CV_Assert(size.width>0 && size.height>0); in imshow()
Fix drawing documentation referring to C API macros
(tab to space) 2x
(typo)
[3rd attempt] fixed HOGDescriptor::detectMultiScale() to group weights as well as ROIs
Reverted back to the previous method where a public method groupRectangles was added to HOGDescriptor to take care of ROI and weight grouping
Added spacing in a nested template argument list.