Ongoing pastes were being abandoned on any key-down event. Quite

Ongoing pastes were being abandoned on any key-down event. Quite
apart from the debatable semantic sanity of abandoning mid-paste,
this was breaking Shift-paste (theoretically valid in any case,
actually necessary with xterm mouse reporting enabled) because when
you hold down Shift the window receives a steady stream of KEYDOWN
messages as the key auto-repeats. One of those is likely to show up
in mid-paste and scupper you. For the moment, this has been changed
so that only a key press that actually _generates session data_
aborts a paste. In future I plan to review just why we're doing this
anyway (it may be that paste-little-by-little was a response to
rubbish socket buffering, in which case we can dispense with it
completely now).

git-svn-id: svn://svn.tartarus.org/sgt/putty@1279 cda61777-01e9-0310-a592-d414129be87e