Added a ring buffer log target to store the last N log messages.

The log target can be used via log alarms and show alarms.
Why? This feature was proposed/requested at
http://openbsc.osmocom.org/trac/wiki/Tasks/ErrorLogTarget
All messages use the same amount of space, prioritizing simplicity.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index be0b5f4..bc9b7de 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -4,7 +4,9 @@
                  smscb/smscb_test bits/bitrev_test a5/a5_test		\
                  conv/conv_test auth/milenage_test lapd/lapd_test	\
                  gsm0808/gsm0808_test gsm0408/gsm0408_test		\
-		 gb/bssgp_fc_test logging/logging_test fr/fr_test
+		 gb/bssgp_fc_test logging/logging_test fr/fr_test	\
+		 loggingrb/loggingrb_test strrb/strrb_test
+
 if ENABLE_MSGFILE
 check_PROGRAMS += msgfile/msgfile_test
 endif
@@ -54,6 +56,12 @@
 fr_fr_test_SOURCES = fr/fr_test.c
 fr_fr_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/src/gb/libosmogb.la
 
+loggingrb_loggingrb_test_SOURCES = logging/logging_test.c
+loggingrb_loggingrb_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/src/vty/libosmovty.la
+
+strrb_strrb_test_SOURCES = strrb/strrb_test.c
+strrb_strrb_test_LDADD = $(top_builddir)/src/libosmocore.la
+
 
 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
@@ -82,7 +90,8 @@
              gb/bssgp_fc_tests.ok gb/bssgp_fc_tests.sh			\
              msgfile/msgfile_test.ok msgfile/msgconfig.cfg		\
              logging/logging_test.ok logging/logging_test.err		\
-             fr/fr_test.ok
+             fr/fr_test.ok loggingrb/logging_test.ok			\
+             loggingrb/logging_test.err	strrb/strrb_test.ok
 
 DISTCLEANFILES = atconfig