WL#814: Creating my.cnf file from server

Add a command to create a my.cnf file from the running server with all
options that doesn't have default values.

Something like:

CREATE OPTION FILE "filename[.cfg]";

This is an alteranative way to handle options compared to task 711

In discussion with Monty and Sergie the suggested language was:
SHOW VARIABLES AS mycnf;

with the possibility of using the INTO OUTFILE syntax possibly for the output to
file.