ob-C, ob-clojure, ob-tangle, org-agenda, org, ox: fix byte-compiler warnings
* lisp/ob-C.el, lisp/ob-clojure.e: Require 'cl at compile-time.
* lisp/ob-tangle.el: Do not require 'cl at compile time.
* lisp/org-agenda.el: Declare function `org-columns-remove-overlays´.
* lisp/org.el: Declare functions `org-clocktable-shift´,
`org-clock-update-time-maybe´, `org-clock-remove-overlays´,
`org-babel-tangle-file´, `org-table-blank-field´,
`org-table-insert-row´, `org-add-archive-files´, `org-table-begin´,
`org-table-end´. Move defsubst `org-uniquify´ before its many uses.
* lisp/ox.el: Move defsubst `org-export-get-parent´ before its many
uses.