parsing: ban strncpy()

Git upstream bans strncpy() with commit:

  banned.h: mark strncpy() as banned
  e488b7aba743d23b830d239dcc33d9ca0745a9ad

Signed-off-by: Christian Hesse <mail@eworm.de>

parsing.c

@@ -63,8 +63,7 @@ static char *substr(const char *head, const char *tail)
 	if (tail < head)
 		return xstrdup("");
 	buf = xmalloc(tail - head + 1);
-	strncpy(buf, head, tail - head);
+	strlcpy(buf, head, tail - head + 1);
-	buf[tail - head] = '\0';
 	return buf;
 }