Correct a whole bunch of bugs coming with renamed cell relocation.

Correct a whole bunch of bugs coming with renamed cell relocation.

* lisp/ses.el (ses-localvars): rename variable
`ses--renamed-cell-symb-list' into `ses--in-killing-named-cell-list'
and adjust the comment about it.
(ses-plist-delq): new defun.
(ses--ses-buffer-list): new defvar.
(ses--unbind-cell-name): new defun.
(ses-relocate-symbol): Do not relocate symbol when it is a named cell.
(ses-relocate-formula): Undo change of
2011-12-27T19:30:39Z!vincentb1@users.sourceforge.net that was
preventing relocation for named cell --- now doing this is delegated
to function `ses-relocate-symbol'.
(ses-relocate-range): In docstring, undo change of
2016-01-03T07:31:52Z!johnw@newartisans.com, `ses-range' must remain
lower case as it is not a variable.
(ses-relocate-all): Cell name relocation : 1) check that cell is a
renamed cell by testing `ses-cell' property to :ses-named, rather than
comparing name to corresponding standard name. Set rowcol of renamed
cell into the hashmap --- `ses-cell' property must not be used for
that as the same name can be used for different locations in different
SES sheets ; 2) use `local-variable-if-set-p' rather than `boundp' and
`local-variable-p' to check if cell name is already in use in this
sheet or needs initialisation.
(ses-relocate-all): Cell value relocation : 1) like for name
relocation use the `ses-cell' property rather than comparing actual
name to corresponding standard name. 2) Correct bug introduced in
2011-12-27T19:30:39Z!vincentb1@users.sourceforge.net, as the test was
made the other way round than the intention --- ie value relocation
was disabled for standard cell, not for renamed cell as was the
intention.
(ses-relocate-all): Add loop for unbinding deleted renamed cells
names.
(ses-killbuffer-hook): new defun.
(ses-mode): Add the ses--ses-buffer-list maintenance mechanism ---
kill buffer hook, plus pushing current buffer if new in list.
(ses-delete-row, ses-delete-column): Collect deleted renamed cells
into `ses--in-killing-named-cell-list'.
(ses-rename-cell): Remove update of variable
`ses--renamed-cell-symb-list', this variable is renamed to
`ses--in-killing-named-cell-list', and its setting is done in
functions `ses-delete-row' and , `ses-delete-column' now.
(ses-rename-cell): Change correction of
2015-12-30T23:10:37Z!vincentb1@users.sourceforge.net concerning
computation of the range over which `cursor-intangible' property was
to be updated. This correction was ok for non spilling cells, but not
for cells spilling over following blank cells. Simply use
`next-single-property-change' rather than computing the end column
from column widths.