Fixing compilation

Patched the saliency module to use ObjectivenessBING bounding box
proposals from python.

Usage:

```
bing = cv2.saliency.ObjectnessBING()
img = cv2.imread('/home/ignotus/Pictures/10376146_973700932714682_2056967515849182952_n.jpg')
bing.computeSaliency(img)
```

The rectangle at top is not having maximum objectness value.

Fixed warnings for XCode 7.1.1 and cmake 3.3.2, rewrote one method in sliency to avoid clang 7.0.0 crash

Adding float casts allows them to compile on MSVC and should not
affect other compilers.

NAN is a compiler specific constant that does not exist on
visual studio. I also noticed that some NAN instances had been
cast to float, whereas quiet_NaN is both 1) defined by the
standard and 2) templated for the correct type. This is a much
more portable method of getting a NaN value.

replaced "const InputArray" with "InputArray" to avoid warnings about "const const _InputArray&"