[PATCH] Show banner in server and client startup to drive community engagement

[PATCH] Show banner in server and client startup to drive community engagement

Suggest to users that they can support MariaDB development by simply giving a
star on GitHub. This patch experiments with how well such a banner works, and
may later change the contents to drive some other kind of engagement.

Client output:
    Welcome to the MariaDB monitor.  Commands end with ; or \g.
    Your MariaDB connection id is 34
    Server version: 10.11.7-MariaDB-3 Debian n/a

    Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
    Support MariaDB developers by giving a star at https://github.com/MariaDB/server

    Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

    MariaDB [(none)]>

Server output:
    [Note] Support MariaDB developers by giving a star at https://github.com/MariaDB/server

Server output if build in git directory:
    [Note] Starting MariaDB 10.11.7-MariaDB-3 source revision 219efb0a6ab0ee8ce2ec831c715783586c4db2ef as process 5426

Gbp-Pq: Name startup-message.patch