moved some old stuff to the legacy module; merge "compat_c.h" headers and moved to the legacy as well. moved implementation of many non-critical/obsolete inline functions and methods to .cpp to improve Opencv build time

fixed canny test; fixed mhi-global test & implementation (hopefully, for the last time); added sse 4.1 & 4.2 support (not working in Xcode for some reason); moved splineInterpolation to color.cpp; fixed a few bugs in documentation