patch 9.0.1969: [security] buffer-overflow in trunc_string()

Problem:  buffer-overflow in trunc_string()
Solution: Add NULL at end of buffer

Currently trunc_string() assumes that when the string is too long,
buf[e-1] will always be writeable. But that assumption may not always be
true. The condition currently looks like this

    else if (e + 3 < buflen)
    [...]
    else
    {
	// can't fit in the "...", just truncate it
	buf[e - 1] = NUL;
    }

but this means, we may run into the last else clause with e still being
larger than buflen. So a buffer overflow occurs.

So instead of using `buf[e - 1]`, let's just always
truncate at `buf[buflen - 1]` which should always be writable.

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 1be1462..3056f35 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1969,
+/**/
     1968,
 /**/
     1967,