The cascade classifier changes its structure on new version of OpenCV.
The need to migrate to C++ to utilize the new load method of OpenCV which
allows to load the new classifiers.
https://bugzilla.gnome.org/show_bug.cgi?id=748377
If old opencv1-style legacy include directory is available,
this change becomes purely cosmetic (maybe will compile a bit faster).
It becomes an FTBFS fix when opencv1-style include directory is missing
(possibly because opencv package maintainer decided not to pack it).
https://bugzilla.gnome.org/show_bug.cgi?id=747705
face detection will be performed only if image standard deviation is
greater that min-stddev. Default min-stddev is 0 for backward
compatibility. This property will avoid to perform face detection on
images with little changes improving cpu usage and reducing false
positives
https://bugzilla.gnome.org/show_bug.cgi?id=730510
