Turns out that the compose-keys fix in r9567 did in fact break one

Turns out that the compose-keys fix in r9567 did in fact break one
piece of keyboard handling: if Num Lock is on, numeric keypad keys are
eaten by the IM, so we must avoid passing them to the IM in the first
place if we're in any non-default numeric keypad mode (application or
Nethack).

This is a grubby way to do it, but the more obvious approach of just
moving the Nethack and app-keypad if statements up to above the IM
call doesn't work because those statements depend on the generic
Alt-prefix handling that happens just _below_ the IM call. So instead
I just repeat the list of keystrokes and modes in an if statement
conditionalising the IM call.

git-svn-id: svn://svn.tartarus.org/sgt/putty@9573 cda61777-01e9-0310-a592-d414129be87e