add functions for bit-reversal

Sometimes we need stuff like reversing every bit in each byte (but not
the byte-order).
diff --git a/tests/bits/Makefile.am b/tests/bits/Makefile.am
new file mode 100644
index 0000000..dd03e83
--- /dev/null
+++ b/tests/bits/Makefile.am
@@ -0,0 +1,6 @@
+INCLUDES = $(all_includes) -I$(top_srcdir)/include
+noinst_PROGRAMS = bitrev_test
+
+bitrev_test_SOURCES = bitrev_test.c
+bitrev_test_LDADD = $(top_builddir)/src/libosmocore.la
+