ofxOpenCv: wrap OpenCV 5, keep OpenCV 4

[danoli3]

What

ofxOpenCv still uses OpenCV's legacy C API (IplImage, cvCopy, CV_INTER_NN, cv::cvarrToMat, cvFindContours, …). OpenCV 5 removed that API entirely, so a system OpenCV 5 install fails to compile the addon.

This showed up on MSYS2 ucrt64 when the pinned OpenCV 4.13.0-7 package could not be fetched and pacman fell back to mingw-w64-ucrt-x86_64-opencv 5.0.0. install_dependencies.sh already rewrote pkg-config to opencv5, then allAddonsExample died on:

• IplImage was not declared
• CV_INTER_NN was not declared
• cv::cvarrToMat was not declared

MSYS2 is still being compiled against OpenCV 4; this is the fallback path.

Approach

Keep the public ofxOpenCv API. Branch on CV_MAJOR_VERSION:

	OpenCV 4	OpenCV 5
Types	real IplImage / CvMat via imgproc_c.h	shim structs over cv::Mat
cv* helpers	OpenCV C API	thin wrappers around cv::resize / cvtColor / …
getCvMat() / Haar / undistort	ofxCvToMat → cv::cvarrToMat	ofxCvToMat → ROI-aware cv::Mat view
contours	cvFindContours + CvSeq	cv::findContours

Haar CascadeClassifier lives in contrib xobjdetect on OpenCV 5; the compat header includes it when present (MSYS2's opencv 5 package ships it).

Also

• addon_config.mk still defaults to opencv4. Install scripts now select opencv5 / opencv4 / opencv from pkg-config (MSYS2 + Linux distros).
• MSYS2 still prefers the pinned 4.x package; 5.x fallback should compile.
• Two CV examples that called cv::cvarrToMat now use getCvMat().

Test plan

• MSYS2 ucrt64 with pinned OpenCV 4.13 (current path)
• MSYS2 ucrt64 with OpenCV 5 fallback (pkg-config opencv5)
• Linux with libopencv-dev / opencv4
• allAddonsExample and opencv contour / Haar examples