Tests: Add a way to write a Weston.ini inside the test

Currently doesn't exist a standard way to write a weston.ini inside a test.

Here, two new functions weston_ini_setup and cfgln are introduced to help the test writer to write a weston.ini file and load it to the test.

To load it, the tester needs to call weston_test_harness_execute_as_client in the same way as before. The weston_ini_setup will fill the setup->config_file with the correct path to the weston.ini file.

Closes:#410 (closed) Signed-off-by: Igor Matheus Andrade Torrente igormtorrente@gmail.com