Added some null function definitions whose purpose is to suppress CRAN 
check notes about the absence of visible bindings. In this case the code
anticipates cases with the absent bindings. Also edited yai() to reduce
some line lengths.


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/yaimpute@72 edb9625f-4e0d-4859-8d74-9fd3b1da38cb