GSM_SystemInformation: Add support for "OTHER" SIs

This way we can process SIs for which we don't have a more detailed
parser code and simply store their L3 as octetstring.
diff --git a/sysinfo/GSM_SystemInformation.ttcn b/sysinfo/GSM_SystemInformation.ttcn
index 1bfc7a4..86cba2a 100644
--- a/sysinfo/GSM_SystemInformation.ttcn
+++ b/sysinfo/GSM_SystemInformation.ttcn
@@ -232,7 +232,8 @@
 		SystemInformationType5		si5,
 		SystemInformationType5bis	si5bis,
 		SystemInformationType5ter	si5ter,
-		SystemInformationType6		si6
+		SystemInformationType6		si6,
+		octetstring			other
 	} with { variant "" };
 
 	type record SystemInformation {
@@ -248,6 +249,7 @@
 			      si5bis, header.message_type = SYSTEM_INFORMATION_TYPE_5bis;
 			      si5ter, header.message_type = SYSTEM_INFORMATION_TYPE_5ter;
 			      si6, header.message_type = SYSTEM_INFORMATION_TYPE_6;
+			      other, OTHERWISE;
 			)" };
 
 	external function enc_SystemInformation(in SystemInformation si) return octetstring