abis: Create a routine that can parse all SW Descriptions of a SW Config

Be able to parse the entire SW Config IE. Parse the SW Descruption
into a struct provided by the caller.
diff --git a/openbsc/.gitignore b/openbsc/.gitignore
index f345bac..bf909f5 100644
--- a/openbsc/.gitignore
+++ b/openbsc/.gitignore
@@ -58,6 +58,7 @@
 tests/sms/sms_test
 tests/timer/timer_test
 tests/gprs/gprs_test
+tests/abis/abis_test
 
 tests/atconfig
 tests/atlocal