Use "mode-line" instead of "modeline".

Use "mode-line" instead of "modeline".

* org-clock.el (org-clock-modeline-total): Make obsolete.
(org-clock-mode-line-total): Rename from
`org-clock-modeline-total'.
(org-clock-get-sum-start): Fix references to
`org-clock-modeline-total'.

* org-faces.el (org-agenda-filter-tags)
(org-agenda-filter-category, mode-line): Use the 'mode-line
face instead of the obsolete 'modeline.

Thanks to Brendan Halpin for reporting this.