gsm0808: Add create functions for BSS_MAP_MSG_PAGING

gsm0808.h/c lacks functionality to generate BSS_MAP_MSG_PAGING messages. These
messages are required if the code is used in an MSC implementation.

This commit adds a gsm0808_create_paging() function, that generates an A/AoiP
BSS_MAP_MSG_PAGING message.

Change-Id: I9afecf0109305ca5153bf081bb29cd94071dd2b7
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 786bf08..ec23418 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -135,6 +135,7 @@
 gsm0808_create_clear_command;
 gsm0808_create_clear_complete;
 gsm0808_create_clear_rqst;
+gsm0808_create_paging;
 gsm0808_create_dtap;
 gsm0808_create_layer3;
 gsm0808_create_layer3_aoip;