CMake: Remove common.cmake

It doesn't contain anything useful
Move warning message about libstdc++ caveats from CMakeLists.txt to README.md
CMake: Add option to build with libc++ if using Clang on Linux
Use <codecvt> substitute code when <codecvt> isn't supported instead of when GCC is compiler
Fixed portals that teleport within the same map
Tweaked view calculations
Removed haste from player

Signed-off-by: Peter Atashian <retep998@gmail.com>
Merge branch 'master' of github.com:NoLifeDev/NoLifeStory
Merge branch 'cmake-improvements' of github.com:crumblingstatue/NoLifeStory