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/Makefile.am

@@ -289,6 +289,8 @@ TESTS_norun += \
 		alsa-time-test
 endif
 
+TESTS_ENVIRONMENT=MAKE_CHECK=1
+
 if BUILD_TESTS_DEFAULT
 noinst_PROGRAMS = $(TESTS) $(TESTS_norun)
 else