Fix the text files end-of-line format globally in the repo

[MartinCupak]

As a fork heritage, It's quite messy with source code being partially in MSDOS end of line format and UNIX end of line format

[MartinCupak]

Git/github must have some setting to get this right regardless the client platform used.

[MartinCupak]

fixed for .h .cpp files, based on these instructions ( recent version of git from ppa needed)

Normalize handling of end-of-line characters

https://help.github.com/en/github/using-git/configuring-git-to-handle-line-endings
https://stackoverflow.com/questions/7156694/git-how-to-renormalize-line-endings-in-all-files-in-all-revisions

[MartinCupak]

created also .gitattributes file:

# Set the default behavior, in case people don't have core.autocrlf set.
* text=auto

# Explicitly declare text files you want to always be normalized and converted
# to native line endings on checkout.
*.cfg text
*.sh text
*.md text
*.in text
*.m4 text
*.cmake text
*.txt text
*.service text
*.py text
*.am text

However, the above does not seem to do anything for explicitly listed files (?)