-extern int lf_sqlperform(uschar *, uschar *, uschar *, uschar *, uschar **,
- uschar **, BOOL *, int(*)(uschar *, uschar *, uschar **,
+extern int lf_sqlperform(const uschar *, const uschar *, const uschar *,
+ const uschar *, uschar **,
+ uschar **, BOOL *, int(*)(const uschar *, uschar *, uschar **,