Submitting multiple changes as R-Forge SVN has been down. Added the use of getOption...

Submitting multiple changes as R-Forge SVN has been down.  Added the use of getOption() to obtain the defaults for print.xtable().  Added the "booktabs" argument as suggested by Matthieu Stigler.  Removed the changes regarding hline handling, as these were work-arounds to enable "booktabs", are no longer needed, and seemed to be causing missing hlines with "longtable" (perhaps only when combined with the booktabs changes).

git-svn-id: svn://scm.r-forge.r-project.org/svnroot/xtable@26 edb9625f-4e0d-4859-8d74-9fd3b1da38cb