forcing -std=c++11 or using CXX_STANDARD is not recommended in a library, since it prevents users to compile the library with a more recent C++ standard.
also remove hardcoded C++ standard from generated pkgconfig file
cxx_std_11 is supported since CMake 3.8, so it's fine since current min CMake version of fcl is 3.10
cxx_std_11
is supported since CMake 3.8, so it's fine since current min CMake version of fcl is 3.10This change is