Support "bracket paste mode" and cursor-style manipulation

Hello, lists

This patch adds the following two features to GNU Screen:

- Bracket Paste Mode (DECSET/DECRST 2004)
- DECSCUSR(cursor style manipulation)

By using "bracketed paste mode", the pasted text is bracketed with special
control sequences.
DECSCUSR can change cursor style and shape (blink/steady, block/Vertical
bar/horizontal bar).

ref: http://invisible-island.net/xterm/ctlseqs/ctlseqs.html

These days, many of xterm-compatible terminal emulators support these features.
But current GNU Screen blocks them.
This patch manages states of "Bracket Paste Mode (DECSET/DECRST 2004)" and
DECSCUSR(cursor style manipulation), for each of screens.

Please check it.

Hayaki Saito <address@hidden>

https://lists.gnu.org/archive/html/screen-devel/2013-03/msg00000.html
bye bye DEBUG
unused function
Small fix
Remove *Rewrite, they mostly return EXPENSIVE anyway
Fix rendition reset