Forgot to comment test number verbose + minor change to dcast

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1186 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
minor edit in tests

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1187 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
MyVar=TRUE; DT[,sum(b,na.rm=MyVar),by=a] is now gforce optimized and tested. Thanks Arun.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1188 edb9625f-4e0d-4859-8d74-9fd3b1da38cb