Allow the level builder to try to place another vault after choosing one

of the smaller minivaults, leading to more interesting vaults.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@10030 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dploog  on June 24, 2009
MHXEKTL6NTYH4MSVCB3M7NFOUD545EEGPOQAAB24SVXGPHUW4TBAC
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