Forward-port the renaming of changes.stone_soup to changelog.txt from

0.5 r10259.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@10260 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dolorous  on July 17, 2009
HP4RJK3VXABKF7KVSLNSY2L4CNMSKHPN3BTZXUTGIK5IPTRJDJRQC
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