Recalculate permanent mutations when changing species, but leave non-permanent

mutations in place.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@5753 c06c8d41-db1a-0410-9941-cceddc491573

Created by  zelgadis  on June 12, 2008
2U7VFZ3242P22EPRQKCIHFZRRWHHBZGOEEN2WJNMCXV5BEI67NNAC
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