add db_subscr_create(), db_subscr_delete(), db_subscr_update_msisdn_by_imsi()

These will be needed by VTY commands to create, delete and modify subscribers.

Auth data editing will follow in another patch.

The FIXME "also remove authentication data from auc_2g and auc_3g" will get
fixed in change-id Icb11b5e059fb920447a9aa414db1819a0c020529.

Change-Id: I725273d36234331093e7fff7d5f12f6be6ab2623
diff --git a/src/db.c b/src/db.c
index 463eeb4..7c25e63 100644
--- a/src/db.c
+++ b/src/db.c
@@ -41,6 +41,9 @@
 	[DB_STMT_UPD_PURGE_PS_BY_IMSI] = "UPDATE subscriber SET ms_purged_ps=1 WHERE imsi = ?",
 	[DB_STMT_SET_NAM_PS_BY_IMSI] = "UPDATE subscriber SET nam_ps=1 WHERE imsi = ?",
 	[DB_STMT_UNSET_NAM_PS_BY_IMSI] = "UPDATE subscriber SET nam_ps=0 WHERE imsi = ?",
+	[DB_STMT_SUBSCR_CREATE] = "INSERT INTO subscriber (imsi) VALUES ($imsi)",
+	[DB_STMT_DEL_BY_ID] = "DELETE FROM subscriber WHERE id = $subscriber_id",
+	[DB_STMT_SET_MSISDN_BY_IMSI] = "UPDATE subscriber SET msisdn = $msisdn WHERE imsi = $imsi",
 };
 
 static void sql3_error_log_cb(void *arg, int err_code, const char *msg)