src/db.c: Switch from "const char *statements" to "const char * const"

This is primarily to make the linter happy, which spews "static const
char * array should probably be static const char * const" errors in
gerrit when adding similar new code to this existing file.  So let's
first convert the old code and then add new code that makes the linter
happy.  I guess it does have a point, as both the individual string
pointers as well as the array of the pointers are constant.

Change-Id: I39e9fb6bd8052f4878cfc95061775bf940631ae5
diff --git a/src/db.c b/src/db.c
index 23dcbbc..cfe34c3 100644
--- a/src/db.c
+++ b/src/db.c
@@ -235,7 +235,7 @@
 	talloc_free(dbc);
 }
 
-static int db_run_statements(struct db_context *dbc, const char **statements, size_t statements_count)
+static int db_run_statements(struct db_context *dbc, const char * const *statements, size_t statements_count)
 {
 	int rc = 0;
 	int i;
@@ -308,7 +308,7 @@
 db_upgrade_v1(struct db_context *dbc)
 {
 	int rc;
-	const char *statements[] = {
+	const char * const statements[] = {
 		"ALTER TABLE subscriber ADD COLUMN last_lu_seen TIMESTAMP default NULL",
 		"PRAGMA user_version = 1",
 	};
@@ -324,7 +324,7 @@
 static int db_upgrade_v2(struct db_context *dbc)
 {
 	int rc;
-	const char *statements[] = {
+	const char * const statements[] = {
 		"ALTER TABLE subscriber ADD COLUMN imei VARCHAR(14)",
 		"PRAGMA user_version = 2",
 	};
@@ -437,7 +437,7 @@
 	"ms_purged_ps," \
 	"last_lu_seen"
 
-	const char *statements[] = {
+	const char * const statements[] = {
 		"BEGIN TRANSACTION",
 		"CREATE TEMPORARY TABLE subscriber_backup" SUBSCR_V3_CREATE,
 		"INSERT INTO subscriber_backup SELECT " SUBSCR_V2_COLUMN_NAMES " FROM subscriber",
@@ -460,7 +460,7 @@
 static int db_upgrade_v4(struct db_context *dbc)
 {
 	int rc;
-	const char *statements[] = {
+	const char * const statements[] = {
 		"ALTER TABLE subscriber ADD COLUMN last_lu_seen_ps TIMESTAMP default NULL",
 		"PRAGMA user_version = 4",
 	};
@@ -476,7 +476,7 @@
 static int db_upgrade_v5(struct db_context *dbc)
 {
 	int rc;
-	const char *statements[] = {
+	const char * const statements[] = {
 		"ALTER TABLE subscriber ADD COLUMN vlr_via_proxy VARCHAR",
 		"ALTER TABLE subscriber ADD COLUMN sgsn_via_proxy VARCHAR",
 		"PRAGMA user_version = 5",
@@ -493,7 +493,7 @@
 static int db_upgrade_v6(struct db_context *dbc)
 {
 	int rc;
-	const char *statements[] = {
+	const char * const statements[] = {
 		"CREATE TABLE ind (\n"
 		"	-- 3G auth IND pool to be used for this VLR\n"
 		"	ind     INTEGER PRIMARY KEY,\n"