config: add missing include for non-glibc after ad6d734d51

src/config.c:477:14: error: use of undeclared identifier 'PATH_MAX'
                        char path[PATH_MAX];
                                  ^

src/config.c

@@ -27,6 +27,7 @@
 #include <stdlib.h>
 #include <assert.h>
 #include <fcntl.h>
+#include <limits.h>
 #include <unistd.h>
 #include "ini.h"
 #include "keys.h"