Enable CMAKE_WARN_DEPRECATED flag
Add macro qtyarp_deprecate_with_cmake_version
Fix missing linking with Qt5::WinMain

Starting from CMake 2.8.11 it can be linked automatically when required
using the CMake policy CMP0020 = NEW.
This will be no longer necessary when minimum cmake version will be
2.8.11 or greater.
For cmake 2.8.10 and previous in needs to be linked explicitly.
Fix relative paths for multi-config generators (i.e. visual studio)
Fix paths in config.h on windows (backslash needs to be escaped)