in cut_line(), set placewewant properly after cutting a line, to avoid a

in cut_line(), set placewewant properly after cutting a line, to avoid a
problem where the screen won't be updated if (a) we're not on the first
page when we cut the line, and (b) immediately after we cut the line, we
hit End to move to the end of the line after it

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2504 35c25a1d-7b9e-4130-9fde-d3aeb78583b8