Add namespace bgsegm, replacement functions and Template class for new
OpenCV versions because these functions have been removed. cvarrToMat() is
added because it is compatible with all versions of OpenCV and the use of
class Mat constructor is eliminated, it is also deprecated in 3.X versions.
Use the namespace cv because some functions are called many times.
This patch keeps compatibility with 2.4
https://bugzilla.gnome.org/show_bug.cgi?id=760473
