vty: Make vty_event dispatch signals and use it in the testcase

The testcase didn't work on Ubuntu 12.04 because vty_create will
directly call vty_event (e.g. not through the plt). This means
that the approach to override vty_event in the testcase failed.

Use the signal interface of libosmocore and make the testcase
use it. The signals can be generally useful as well.
4 files changed