Deb: provide the libmysqlclient shim packages that exist in Debian/Ubuntu

This way all 3rd party apps configured to build against any MySQL or
MariaDB version will pick up the libmariadb3-dev package instead.

debian/control

@@ -47,7 +47,7 @@ Conflicts: mariadb-galera-server-10.0 (<< 10.0.5),
            mariadb-server-5.3,
            mariadb-server-5.5 (<< 5.5.33)
 Replaces: libmariadbclient18
-Provides: libmariadbclient18
+Provides: libmariadbclient18, default-libmysqlclient-dev, libmariadbclient-dev-compat
 Description: MariaDB database client library
  MariaDB is a fast, stable and true multi-user, multi-threaded SQL database
  server. SQL (Structured Query Language) is the most popular database query