fixing cap_pvpapi interface and making sure both AVT Manta and Proscilla
series are supported. Testing this with both cams for Windows and Linux
exhaustively.

Optimizing memory footprint by removing unused calls.

Adapted with the input of Shai

Added small example that illustrates how it should work.
Merge pull request #3322 from StevenPuttemans:fix_pvpapi_interface
Suppress a bogus -Warray-bounds in modules/superres/src/optical_flow.cpp

This is actually the same warning that the suppression at the bottom
suppresses, but that one doesn't suppress it when using a native compiler
(go figure).

I remove the forced inclusion of precompiled headers into all sources,
since otherwise this workaround doesn't work - the header with the warning
is included before I can use a pragma.
Merge pull request #3401 from SpecLad:optflow-bogus-Warray-bounds
done