/usr/share/doc/libmono-microsoft-build2.0-cil/changelog.Debian.gz is in libmono-microsoft-build2.0-cil 3.2.8+dfsg-4ubuntu1.
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It is a symlink to /usr/share/doc/libmono-microsoft-build2.0-cil/../libmono-corlib2.0-cil/changelog.Debian.gz