[FIX] CMake: added variable CXX11_STL_FOUND to check for C++11 STL support
[FIX] Yara: check C++11 STL support
[DOC] CMake: mentioned the correct Visual Studio vesion
[FIX] FindCXX11.cmake: removed a typo
Merge pull request #670 from esiragusa/fix/cxx11_stl

CMake checks for C++11 STL