fix [#35795] Edge split modifier do not show result in viewport with curves.

caused by recent changes in normal calculation, however curves were not being very smart about calculating modifiers (calling unneeded re-tessellation for every modifier)


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57566 954f8c5b-7b00-dc11-b283-0030488c597c