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/Makefile.am b/src/Makefile.am
index 09e9101..380e34a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -111,7 +111,7 @@
 db_bootstrap.h: $(BOOTSTRAP_SQL) $(srcdir)/db_sql2c.sed
 	echo "/* DO NOT EDIT THIS FILE. It is generated from files in osmo-hlr.git/sql/ */" > "$@"
 	echo "#pragma once" >> "$@"
-	echo "static const char *stmt_bootstrap_sql[] = {" >> "$@"
+	echo "static const char * const stmt_bootstrap_sql[] = {" >> "$@"
 	cat "$(BOOTSTRAP_SQL)" \
 		| sed -f "$(srcdir)/db_sql2c.sed" \
 		>> "$@"