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/range.c b/range.c
index aef7453..41c6a35 100644
--- a/range.c
+++ b/range.c
@@ -66,7 +66,7 @@
 
 #define setmember(obj, field) ( (obj) . field = field )
 
-static char *nfmtstr(int n, char *fmt, ...) {
+static char *nfmtstr(int n, const char *fmt, ...) {
     va_list va;
     char *ret = snewn(n+1, char);
     va_start(va, fmt);