Extend documentation for Embedded server option mariadb_embedded_options

Do not specify explicit language subdir in --language= argument as it
breaks multi language support or explicit language selection via SQL
command "SET lc_messages = 'ja_JP'" (it does not signal any error).

Add information about --log-error= argument and why it is suggested to
always specify it.

Author: pali

lib/DBD/MariaDB.pod

@@ -364,15 +364,20 @@ Example:
 
   use DBI;
   my $datadir = '/var/lib/mysql/';
-  my $langdir = '/usr/share/mysql/english';
+  my $langdir = '/usr/share/mysql/';
   my $dsn = 'DBI:MariaDB:host=embedded;database=test;'
-          . "mariadb_embedded_options=--datadir=$datadir,--language=$langdir";
+          . "mariadb_embedded_options=--datadir=$datadir,'
+          .                          '--language=$langdir,'
+          .                          '--log-error=/dev/null";
   my $dbh = DBI->connect($dsn, undef, undef);
 
 This would start embedded server with language directory C<$langdir>, database
-directory C<$datadir> and connects to database C<test>. Embedded server does not
-have to be supported by configured MariaDB or MySQL library. In that case
-L<C<< DBI->connect() >>|/connect> returns an error.
+directory C<$datadir>, drop error messages and connects to database C<test>.
+It is suggested to specify C<--log-error=> option which defines location for
+warning messages because by default Embedded server prints its warning and
+error messages to C<STDOUT> which is not expected by Perl or application.
+Embedded server does not have to be supported by configured MariaDB or MySQL
+library. In that case L<C<< DBI->connect() >>|/connect> returns an error.
 
 =item mariadb_embedded_groups