Ensure that source files contain only valid UTF8 encodings (#2188)

Modern software (including text editors, static analysis software,
and web-based code review interfaces) often requires source code files
to be interpretable via a consistent character encoding, with UTF-8 or
ASCII (a strict subset of UTF-8) as the default. Several of the MariaDB
source files contain bytes that are not valid in either the UTF-8 or
ASCII encodings, but instead represent strings encoded in the
ISO-8859-1/Latin-1 or ISO-8859-2/Latin-2 encodings.

These inconsistent encodings may prevent software from correctly
presenting or processing such files. Converting all source files to
valid UTF8 characters will ensure correct handling.

Comments written in Czech were replaced with lightly-corrected
translations from Google Translate. Additionally, comments describing
the proper handling of special characters were changed so that the
comments are now purely UTF8.

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer
Amazon Web Services, Inc.

Co-authored-by: Andrew Hutchings <andrew@linuxjedi.co.uk>

storage/connect/domdoc.cpp

@@ -642,7 +642,6 @@ bool DOMNODELIST::DropItem(PGLOBAL g, int n)
 	if (Listp == NULL || Listp->length < n)
 		return true;
 
-//Listp->item[n] = NULL;  La propriété n'a pas de méthode 'set'
   return false;
 }  // end of DeleteItem