Pinpad input problem for GemPC Pinpad reader

[NIIBE Yutaka]

On 2013-01-11 at 11:43 +0900, NIIBE Yutaka wrote:
> This is due to a bug which doesn't hold lock for _keypad functions.
> 
> Here is a patch to fix this (against master).  Same should be applied
> to 2.0.
> 
> OK to commit?

Sorry, I accidentally pushed this change to master branch without
confirmation, when I pushed scd-work branch.

If this change is not good I will revert.  If not, I'd like to
apply this to 2.0, too.
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