Make config_lines_eq() take const arguments.

src/lib/encoding/confline.c

@@ -256,7 +256,7 @@ config_lines_dup_and_filter(const config_line_t *inp,
 /** Return true iff a and b contain identical keys and values in identical
  * order. */
 int
-config_lines_eq(config_line_t *a, config_line_t *b)
+config_lines_eq(const config_line_t *a, const config_line_t *b)
 {
   while (a && b) {
     if (strcasecmp(a->key, b->key) || strcmp(a->value, b->value))

src/lib/encoding/confline.h

@@ -50,7 +50,7 @@ const config_line_t *config_line_find(const config_line_t *lines,
                                       const char *key);
 const config_line_t *config_line_find_case(const config_line_t *lines,
                                            const char *key);
-int config_lines_eq(config_line_t *a, config_line_t *b);
+int config_lines_eq(const config_line_t *a, const config_line_t *b);
 int config_count_key(const config_line_t *a, const char *key);
 void config_free_lines_(config_line_t *front);
 #define config_free_lines(front) \