fixing cap_pvpapi interface

This PR tries to fix the following 3 reported issues
- http://code.opencv.org/issues/3946
- http://code.opencv.org/issues/3947
- http://code.opencv.org/issues/3948

A complete remake of the PvAPI API interface solving bugs but also
- allowing the use of MANTA type cameras
- allowing multiple AVT cameras at the same time
I think this is defined earlier for non-Windows platforms and and uses the nanosleep() function. 
See line 119:
<pre>
#ifndef WIN32
void CvCaptureCAM_PvAPI::Sleep(unsigned int time)
{
    struct timespec t,r;

    t.tv_sec    = time / 1000;
    t.tv_nsec   = (time % 1000) * 1000000;

    while(nanosleep(&t,&r)==-1)
        t = r;
}
#endif
</pre>