tests: More useful output of make check

Instead of spilling thousands of lines of output, make check now runs the
test-suite in about 100 lines or so.  If running under make check, the output of
tests is reduced. The MAKE_CHECK environment variable is used for this, so that
when running the test manually, the full output is still shown.  Furthermore,
pa_log is used consistently instead of printf, so that all test output goes to
stderr by default.  Colored output from make check goes to stdout.

src/tests/thread-mainloop-test.c

@@ -67,8 +67,6 @@ int main(int argc, char *argv[]) {
     fprintf(stderr, "waiting 5s (sleep)\n");
     pa_msleep(5000);
 
-    fprintf(stderr, "shutting down\n");
-
     pa_threaded_mainloop_stop(m);
 
     pa_threaded_mainloop_free(m);