fix format-overflow error

Reduced the number of characters for representing the size
of a file to 23. That number was choosen so that up to
999,999,999,999,999,999 bytes or ~999 pb can be
represented including commata.

xwin.c

@@ -210,6 +210,9 @@ static char defaultTranslations[] = "\
     ALL_UNUSED_IMPL(VA_NUM_ARGS(__VA_ARGS__)) \
     (__VA_ARGS__)
 
+/* Assuming that there will never be a file lager than 999 petabytes. */
+#define MAX_NUMBER_LABEL_LENGTH 23
+
 /*
  * action routines
  */
@@ -500,7 +503,7 @@ void xrepaint()
 
 void readable_float(float number, char* number_label)
 {
-    char number_string[1024];
+    char number_string[MAX_NUMBER_LABEL_LENGTH];
     int i, j, length;
     sprintf(number_string, "%.2f", number);
     length = (strlen(number_string) - 4) / 3 + strlen(number_string);
@@ -517,7 +520,7 @@ void readable_float(float number, char* number_label)
 
 void readable_long_long(long long number, char* number_label)
 {
-    char number_string[1024];
+    char number_string[MAX_NUMBER_LABEL_LENGTH];
     int i, j, length;
     sprintf(number_string, "%lld", number);
     length = (strlen(number_string) - 1) / 3 + strlen(number_string);
@@ -537,7 +540,7 @@ void xdrawrect(char* name, long long size, int x, int y, int width, int height)
     int textx,
         texty;
     char label[1024];
-    char number_label[1024];
+    char number_label[MAX_NUMBER_LABEL_LENGTH];
     XCharStruct overall;
     int ascent,
         descent,