smpp: Move the coding/mode detection into a utils file
Make sure to not ever have issues with this code again, move the
utility code to a new file and create a basic testcase. The method
currently has 100% line and branch coverage. My initial patched
missed the smpp_utils.c file and I re-did the copying (and verifying
the branch coverage)
diff --git a/openbsc/tests/atlocal.in b/openbsc/tests/atlocal.in
index 0ce168b..bfbecd4 100644
--- a/openbsc/tests/atlocal.in
+++ b/openbsc/tests/atlocal.in
@@ -1 +1,2 @@
enable_nat_test='@osmo_ac_build_nat@'
+enable_smpp_test='@osmo_ac_build_smpp@'