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.err b/tests/gsup/gsup_test.err
index 6cd8627..05c64fe 100644
--- a/tests/gsup/gsup_test.err
+++ b/tests/gsup/gsup_test.err
@@ -13,8 +13,8 @@
   generated message: 05 01 08 21 43 65 87 09 21 43 f5 02 01 07 
   original message:  05 01 08 21 43 65 87 09 21 43 f5 02 01 07 
   IMSI:              123456789012345
-  generated message: 06 01 08 21 43 65 87 09 21 43 f5 08 07 91 94 61 46 32 24 43 09 07 91 83 52 38 48 83 93 04 00 05 15 10 01 01 11 02 f1 21 12 09 04 74 65 73 74 03 61 70 6e 13 01 02 05 11 10 01 02 11 02 f1 21 12 08 03 66 6f 6f 03 61 70 6e 
-  original message:  06 01 08 21 43 65 87 09 21 43 f5 08 07 91 94 61 46 32 24 43 09 07 91 83 52 38 48 83 93 04 00 05 15 10 01 01 11 02 f1 21 12 09 04 74 65 73 74 03 61 70 6e 13 01 02 05 11 10 01 02 11 02 f1 21 12 08 03 66 6f 6f 03 61 70 6e 
+  generated message: 06 01 08 21 43 65 87 09 21 43 f5 08 07 91 94 61 46 32 24 43 09 07 91 83 52 38 48 83 93 04 00 05 19 10 01 01 11 02 f1 21 12 09 04 74 65 73 74 03 61 70 6e 13 01 02 14 02 ff 23 05 11 10 01 02 11 02 f1 21 12 08 03 66 6f 6f 03 61 70 6e 14 02 ae ff 
+  original message:  06 01 08 21 43 65 87 09 21 43 f5 08 07 91 94 61 46 32 24 43 09 07 91 83 52 38 48 83 93 04 00 05 19 10 01 01 11 02 f1 21 12 09 04 74 65 73 74 03 61 70 6e 13 01 02 14 02 ff 23 05 11 10 01 02 11 02 f1 21 12 08 03 66 6f 6f 03 61 70 6e 14 02 ae ff 
   IMSI:              123456789012345
   generated message: 1c 01 08 21 43 65 87 09 21 43 f5 06 01 00 
   original message:  1c 01 08 21 43 65 87 09 21 43 f5 06 01 00 
@@ -45,7 +45,7 @@
   message 2: tested 83 truncations, 81 parse failures
   message 3: tested 11 truncations, 11 parse failures
   message 4: tested 14 truncations, 13 parse failures
-  message 5: tested 73 truncations, 68 parse failures
+  message 5: tested 81 truncations, 75 parse failures
   message 6: tested 14 truncations, 13 parse failures
   message 7: tested 14 truncations, 13 parse failures
   message 8: tested 11 truncations, 11 parse failures
@@ -60,7 +60,7 @@
   message 2: tested 21248 modifications, 2571 parse failures
   message 3: tested 2816 modifications, 510 parse failures
   message 4: tested 3584 modifications, 768 parse failures
-  message 5: tested 18688 modifications, 3505 parse failures
+  message 5: tested 20736 modifications, 4010 parse failures
   message 6: tested 3584 modifications, 769 parse failures
   message 7: tested 3584 modifications, 768 parse failures
   message 8: tested 2816 modifications, 510 parse failures