Fix broken sewer messaging (dpeg).

Fixed bad bounds checks for minivaults placed by dgn_place_map.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@7716 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dshaligram  on December 1, 2008
7DLDFEEB5IHCPN5VL2BBI7JM6SJB6M6FTYM2DMM6R6QV33COOA6QC
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