This commit increase warning level from `W3` to `W4` on MSVC and sets
warnings as errors. Exclusion is made for a specific warning (C4189).

* Use "nullptr" instead of "NULL"

* Cosmetic fix

* bind2nd() and ptr_fun<>() is removed since C++17

bind2nd() and ptr_fun<>() are deprecated in C++11, and removed in C++17.
These functions are not available in LLVM's "libc++".
Use C++11 lambda expressions for them.

* Break long lines

* Add missing header for std::iswspace()