Updated changelog.txt according to the changes of r1980.

git-svn-id: http://corsix-th.googlecode.com/svn/trunk@1982 c39591fa-788f-11de-a72b-d90af8dea425
Did some things wrong with updating changelog.txt.

git-svn-id: http://corsix-th.googlecode.com/svn/trunk@1983 c39591fa-788f-11de-a72b-d90af8dea425