Treat DEL(\x7f) as a control character

[saitoha]

It seems that iTerm2 is able to invoke US-ASCII or DEC Special set into GL area. Both of them are 94 character sets. So \x7f should be treated as a control character(DEL).

Now, the following code prints "abc de" on iTerm2.

echo -e "abc\x7fde"

But it will be "abcde" on most terminals(such as xterm, Terminal.app). This patch improves the compatibility among iTerm2 and them.

[gnachman]

Thanks!