dinput: fix mouse jitter in Halo (bug 7640)

[Martin Traverse]

Hello,

I have done a bisection on bug #7640, mouse jitter in Halo which rendered the 
game unplayable. I have a patch which fixes the problem on my Gentoo system 
against wine-0.9.35.

Bug is introduced by
commit b22ff8018aca7c365e505f1db7732f7050ae259b
dinput: Remove MsgWaitForMultipleObjects call

(Note: commit --59b also severely slows dinput response, fixed soon after by
commit 685a3e6a6ed623718f640e8906bd44fbca3d8b2c
dinput: Release critical section before warping mouse)

Bug can be alleviated by reverting the original commit until
commit af71538d3343a1cec73e75391a7ebfd5b3ed94ee
dinput: Remove duplicate Keyboard->Poll it is the same as base class

I put back the specialised version of Poll with MsgWaitForMultipleObjects,
which fixed the problem, and have sent a patch. It was only necessary to alter 
Poll, not GetDeviceState. This is the first time I've sent in a patch, 
obviously I'm not familiar with the code so I'd be grateful for any comments.

Martin.