Make the code base clean under -Wwrite-strings.

I've also added that warning option and -Werror to the build script,
so that I'll find out if I break this property in future.

1 files changed, 1 insertions, 1 deletions

diff --git a/fifteen.c b/fifteen.c
index 9c83756..f749e96 100644
--- a/fifteen.c
+++ b/fifteen.c
@@ -273,7 +273,7 @@ static char *new_game_desc(const game_params *params, random_state *rs,
 static const char *validate_desc(const game_params *params, const char *desc)
 {
     const char *p;
-    char *err;
+    const char *err;
     int i, area;
     int *used;