Follow convention to have orderning numbers in conf.d folders

All default config files are prepended with '50-'. Admins may
add their custom configs with prepended with higher or lower numbers.
If there is no number at all, the custom configs will be parsed
as the last files.

debian/mariadb-client-10.0.install

 debian/additions/innotop/innotop usr/bin/
-debian/additions/mariadb.conf.d/client.cnf etc/mysql/mariadb.conf.d
+debian/additions/mariadb.conf.d/50-client.cnf etc/mysql/mariadb.conf.d
+debian/additions/mariadb.conf.d/50-mysql-clients.cnf etc/mysql/mariadb.conf.d
 debian/additions/mysqlreport usr/bin/
 usr/bin/mysql_find_rows
 usr/bin/mysql_fix_extensions

debian/mariadb-server-10.0.install

 debian/additions/debian-start etc/mysql
 debian/additions/debian-start.inc.sh usr/share/mysql
 debian/additions/echo_stderr usr/share/mysql
-debian/additions/mariadb.conf.d/server.cnf etc/mysql/mariadb.conf.d
-debian/additions/mariadb.conf.d/mysqld_safe.cnf etc/mysql/mariadb.conf.d
+debian/additions/mariadb.conf.d/50-server.cnf etc/mysql/mariadb.conf.d
+debian/additions/mariadb.conf.d/50-mysqld_safe.cnf etc/mysql/mariadb.conf.d
 etc/apparmor.d/usr.sbin.mysqld
 usr/bin/aria_chk
 usr/bin/aria_dump_log