in display_string(), *really* avoid a memory corruption problem by

allocating enough space for (COLS + 1) characters


git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@3034 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

src/winio.c

@@ -2328,7 +2328,7 @@ char *display_string(const char *buf, size_t start_col, size_t len, bool
     assert(column <= start_col);
 
     /* Allocate enough space for the entire line. */
-    alloc_len = (mb_cur_max() * COLS);
+    alloc_len = (mb_cur_max() * (COLS + 1));
 
     converted = charalloc(alloc_len + 1);
     index = 0;