bug#6456: 24.0.50; quoted-insert not working properly for many keys

[Tim Van Holder <tim.vanholder@gmail.com>]

In current bzr trunk, quoted-insert is not working properly. After
pressing C-q, there are several keys that, when pressed, cause the
insertion of a NUL character (^@) followed by processing the key's
active binding.
Some of the keys in question: [tab], [enter], [kp-enter], [pause],
[escape], [f2], [Scroll_Lock], ...
For some keys like [pause] and [Scroll_Lock] I can see that there is not
really a key to insert, but then my expectation would be that nothing is
inserted and perhaps an error is issued by quoted-insert.
For keys like [tab] and [enter] this is genuinely annoying. Most of my
uses of C-q are to insert a TAB character in modes where TAB is mapped
to an indentation function, of for inserting a CR. Granted, C-q C-i and
C-q C-m still work for this purpose, but [tab] and [return] are far more
"natural" ways to enter these.

Tested with emacs -Q as well, so it's not a configuration issue.

In GNU Emacs 24.0.50.15 (i686-pc-linux-gnu, GTK+ Version 2.8.20)
 of 2010-06-18 on leeloo
Windowing system distributor `The Cygwin/X Project', version 11.0.10503000
configured using `configure  '--with-x''