primary habitat of water instead of a generic one.
git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@7217 c06c8d41-db1a-0410-9941-cceddc491573
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TJN537N2F5J7JWBCT2Z4VSTNXIMFCMEXTKTY7N2UCXIVUUQ3XJBQC
K2CS6TCX2NDVL2ASEHGP4J4K4IJ6FP3ANNKTSIWVG43HPYSBX6ZQC
else if (mermaid && mons_habitat(monster) == HT_WATER
else if (mermaid && mons_primary_habitat(monster) == HT_WATER