+ Extra PROTECT around nested R_MakeExternalPtr, for --enable-strict-barrier.
+ tl reset moved from alloccol into selfrefok (when not ok)
+ write.table(DT) test with bit64 back on, test 897.
+ Tidied checks in init.c
+ Passes Rdevel CMD check

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1182 edb9625f-4e0d-4859-8d74-9fd3b1da38cb