add functions for bit-reversal

Sometimes we need stuff like reversing every bit in each byte (but not
the byte-order).
diff --git a/configure.ac b/configure.ac
index ef4b0aa..f624f2a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -123,6 +123,7 @@
 	tests/msgfile/Makefile
 	tests/ussd/Makefile
 	tests/smscb/Makefile
+	tests/bits/Makefile
 	utils/Makefile
 	Doxyfile.core
 	Doxyfile.gsm