Fix recursive loops for flushing messages when more() is calling getch()

by adding a boolean to keep track on whether we already called flush_prev_message() this round, reset once a new message is pushed into prev_message. There's probably a better solution, but this one works well enough.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@9285 c06c8d41-db1a-0410-9941-cceddc491573

Created by  j-p-e-g  on February 28, 2009
C4R362MEHRAO72H5ZS7K7P66W76AKKDBLDOQQKHV2PHVH5EST6VQC
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