gsup: Add encoding/decoding for the pdp charging characteristics

These fields can be in the ISD and the PDP Context inofmration. Store
pointers to this IE in both cases. It needs to be used by the SGSN
when opening a PDP context.

Change-Id: Iedc7c02adcf77ca5c9545119e19c968dfbbb3e6b
diff --git a/tests/gsup/gsup_test.c b/tests/gsup/gsup_test.c
index a950ca3..3b360ac 100644
--- a/tests/gsup/gsup_test.c
+++ b/tests/gsup/gsup_test.c
@@ -69,15 +69,18 @@
 		0x09, 0x07, /* HLR-Number of the subscriber */
 			0x91, 0x83, 0x52, 0x38, 0x48, 0x83, 0x93,
 		0x04, 0x00, /* PDP info complete */
-		0x05, 0x15,
+		0x05, 0x19,
 			0x10, 0x01, 0x01,
 			0x11, 0x02, 0xf1, 0x21, /* IPv4 */
 			0x12, 0x09, 0x04, 't', 'e', 's', 't', 0x03, 'a', 'p', 'n',
 			0x13, 0x01, 0x02,
+			0x14, 0x02, 0xFF, 0x23,
 		0x05, 0x11,
 			0x10, 0x01, 0x02,
 			0x11, 0x02, 0xf1, 0x21, /* IPv4 */
 			0x12, 0x08, 0x03, 'f', 'o', 'o', 0x03, 'a', 'p', 'n',
+		0x14, 0x02,
+			0xAE, 0xFF
 	};
 
 	static const uint8_t location_cancellation_req[] = {