xapian-bridge C port

endlessm/eos-sdk#2463
optional: To avoid tedious repetitions I usually do something like this:

```c
#define ADD_DAEMON_TEST(name, func) g_test_add((name), DaemonFixture, NULL, setup, (func), teardown);
ADD_DAEMON_TEST ("/daemon/starts-successfully", test_daemon_starts_successfully);
...
#undef ADD_DAEMON_TEST
```