logging: Move the logging test from OpenBSC into libosmocore

Add a testcase for the logging facility. The test is coming from
the OpenBSC code.
diff --git a/tests/logging/logging_test.err b/tests/logging/logging_test.err
new file mode 100644
index 0000000..b59d2e8
--- /dev/null
+++ b/tests/logging/logging_test.err
@@ -0,0 +1,3 @@
+You should see this
+You should see this
+
\ No newline at end of file