MDEV-19169: Add --defaults-group-suffix option to mysql_install_db man page

man/mysql_install_db.1

 '\" t
 .\"
-.TH "\FBMYSQL_INSTALL_DB\" "1" "14/12/2015" "MariaDB 10\&.1" "MariaDB Database System"
+.TH "\FBMYSQL_INSTALL_DB\FR" "1" "4 April 2019" "MariaDB 10\&.1" "MariaDB Database System"
 .\" -----------------------------------------------------------------
 .\" * set default formatting
 .\" -----------------------------------------------------------------
@@ -198,6 +198,21 @@ Must be given as first option\&.
 .sp -1
 .IP \(bu 2.3
 .\}
+.\" mysql_install_db: defaults-group-suffix option
+.\" defaults-group-suffix option: mysql_install_db
+\fB\-\-defaults\-group\-suffix=\fR\fB\fIname\fR\fR
+.sp
+In addition to the given groups, also read groups with this suffix\&.
+.RE
+.sp
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
 .\" mysql_install_db: force option
 .\" force option: mysql_install_db
 \fB\-\-force\fR
@@ -354,7 +369,7 @@ For internal use\&. This option is used for creating Windows distributions\&.
 .SH "COPYRIGHT"
 .br
 .PP
-Copyright 2007-2008 MySQL AB, 2008-2010 Sun Microsystems, Inc., 2010-2015 MariaDB Foundation
+Copyright 2007-2008 MySQL AB, 2008-2010 Sun Microsystems, Inc., 2010-2019 MariaDB Foundation
 .PP
 This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.
 .PP