Experimentally mark the Alt key as unpressed everytime we get a

CMD_NO_CMD result with Tiles in case it's the result of the Alt-Tab bug.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@10421 c06c8d41-db1a-0410-9941-cceddc491573

Created by  j-p-e-g  on July 26, 2009
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