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 "L" notation for wide character

* Remove unneeded cast

PrintMessage() now uses const pointer

* C++11 accepts std::string for std::wifstream

* C++11 accepts std::string for std::wifstream

* Use mbstowcs()/wcstombs() to convert character class

This fix works when file path includes non-ASCII characters.

* Revert "Use mbstowcs()/wcstombs() to convert character class"

This reverts commit 7fd150a1570b8d6de246da352688daaeadcda998.

mbstowcs()/wcstombs() is not so secure, and recommends mbstowcs_s()/wcstombs_s().
But these secure variants are not supported by some C libraries.

* Enable warnings

* Work without "-fpermissive" option

* Cosmetic fix

* Add "const" to fix warnings

These strings are not needs to modify.

* No need to use "#pragma once" in main C++ source file

* Cosmetic fix

Add newline to end

* Return nullptr if error

* delete() not works for "void*"

Cast specific type to use delete()

* Disable VC++ specific pragmas for other C++ compilers

* Fix warning

* Fix warning

* Use pipeline for compiler

* Enable code optimization

* Add "default:" to fix "switch" syntax warning

* Use "nullptr" for null pointer

* Use nullptr instead of NULL

* Use nullptr instead of NULL

* Use "L" notation for wide character

* Use C++ header instead of raw C header

Remove openFile entirely to avoid latent problems with stream copy semantics.

Several classes and functions were not const-correct. Did the minimal changes
to fix compilation, although there are other const fixes that can be done.

- replaced for_each with range-based for loop
- added missing std:: scope
- for-loop temp now declared outside the loop to be in scope
- removed casts in calls to trim()