babel: small change in API.

babel: small change in API.

* lisp/ob-core.el (org-babel--get-vars): New function.
(org-babel-get-header): Delete.
* lisp/ob-C.el (org-babel-C-expand-C):
(org-babel-C-expand-D):
* lisp/ob-R.el (org-babel-variable-assignments:R):
* lisp/ob-abc.el (org-babel-expand-body:abc):
* lisp/ob-asymptote.el (org-babel-variable-assignments:asymptote):
* lisp/ob-awk.el (org-babel-execute:awk):
* lisp/ob-calc.el (org-babel-execute:calc):
* lisp/ob-clojure.el (org-babel-expand-body:clojure):
* lisp/ob-dot.el (org-babel-expand-body:dot):
* lisp/ob-emacs-lisp.el (org-babel-expand-body:emacs-lisp):
* lisp/ob-fortran.el (org-babel-expand-body:fortran):
(org-babel-fortran-ensure-main-wrap):
* lisp/ob-gnuplot.el (org-babel-gnuplot-process-vars):
* lisp/ob-haskell.el (org-babel-variable-assignments:haskell):
* lisp/ob-js.el (org-babel-variable-assignments:js):
* lisp/ob-latex.el (org-babel-expand-body:latex):
* lisp/ob-lilypond.el (org-babel-expand-body:lilypond):
* lisp/ob-lisp.el (org-babel-expand-body:lisp):
* lisp/ob-maxima.el (org-babel-maxima-expand):
* lisp/ob-ocaml.el (org-babel-variable-assignments:ocaml):
* lisp/ob-octave.el (org-babel-variable-assignments:octave):
* lisp/ob-org.el (org-babel-expand-body:org):
* lisp/ob-perl.el (org-babel-variable-assignments:perl):
* lisp/ob-picolisp.el (org-babel-expand-body:picolisp):
* lisp/ob-processing.el (org-babel-variable-assignments:processing):
* lisp/ob-python.el (org-babel-variable-assignments:python):
* lisp/ob-ruby.el (org-babel-variable-assignments:ruby):
* lisp/ob-scheme.el (org-babel-expand-body:scheme):
* lisp/ob-shell.el (org-babel-variable-assignments:shell):
* lisp/ob-shen.el (org-babel-expand-body:shen):
* lisp/ob-sql.el (org-babel-expand-body:sql):
* lisp/ob-sqlite.el (org-babel-expand-body:sqlite): Adapt to change.
* etc/ORG-NEWS: Document change.