tests: Disable tests that rely on ceil() on CLR

CLR x64 JIT does not implement ceil() properly (ceil(-0.1) returns
positive zero instead of negative zero). Disable the relevant portions of
tests so that everything else is green...

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1062 99668b35-9821-0410-8761-19e4c4f06640