Change "#pragma once" to "#ifndef FILE_NAME_EXT" guard

[ivancea]

Original report by Iván Cea (Bitbucket: ivancea, GitHub: ivancea).

---

#!c++

#pragma once

to

#!c++

#ifndef FILE_NAME_EXT
#define FILE_NAME_EXT
// ...
#endif FILE_NAME_EXT

[ivancea]

Original comment by Iván Sanz (Bitbucket: ivansanz, GitHub: isc30).

---

Extension not needed. I propose something like:

#ifndef FILENAME
#define FILENAME
// ...
#endif FILENAME