ob-C: unified naming of "c++" functions/variables to "C++"

  Thanks to Martyn Jago for this patch

* lisp/ob-C.el (org-babel-tangle-lang-exts): Replace "c++" with "C++".
  (org-babel-C++-compiler): Replace "c++" with "C++".
  (org-babel-execute:cpp): Replace "c" with "C++".
  (org-babel-execute:C++): Replace "c" with "C++".
  (org-babel-expand-body:C++): Replace "c" with "C++".
  (org-babel-C-execute): Replace "c" with "C++".

lisp/ob-C.el

@@ -38,7 +38,7 @@
 (declare-function org-entry-get "org"
 		  (pom property &optional inherit literal-nil))
 
-(add-to-list 'org-babel-tangle-lang-exts '("c++" . "cpp"))
+(add-to-list 'org-babel-tangle-lang-exts '("C++" . "cpp"))
 
 (defvar org-babel-default-header-args:C '())
 
@@ -46,8 +46,8 @@
   "Command used to compile a C source code file into an
   executable.")
 
-(defvar org-babel-c++-compiler "g++"
-  "Command used to compile a c++ source code file into an
+(defvar org-babel-C++-compiler "g++"
+  "Command used to compile a C++ source code file into an
   executable.")
 
 (defvar org-babel-c-variant nil
@@ -56,15 +56,15 @@ is currently being evaluated.")
 
 (defun org-babel-execute:cpp (body params)
   "Execute BODY according to PARAMS.  This function calls
-`org-babel-execute:C'."
-  (org-babel-execute:C body params))
+`org-babel-execute:C++'."
+  (org-babel-execute:C++ body params))
 
-(defun org-babel-execute:c++ (body params)
+(defun org-babel-execute:C++ (body params)
     "Execute a block of C++ code with org-babel.  This function is
 called by `org-babel-execute-src-block'."
   (let ((org-babel-c-variant 'cpp)) (org-babel-C-execute body params)))
 
-(defun org-babel-expand-body:c++ (body params)
+(defun org-babel-expand-body:C++ (body params)
   "Expand a block of C++ code with org-babel according to it's
 header arguments (calls `org-babel-C-expand')."
   (let ((org-babel-c-variant 'cpp)) (org-babel-C-expand body params)))
@@ -81,7 +81,7 @@ header arguments (calls `org-babel-C-expand')."
 
 (defun org-babel-C-execute (body params)
   "This function should only be called by `org-babel-execute:C'
-or `org-babel-execute:c++'."
+or `org-babel-execute:C++'."
   (let* ((tmp-src-file (org-babel-temp-file
 			"C-src-"
 			(cond
@@ -98,7 +98,7 @@ or `org-babel-execute:c++'."
 	     (format "%s -o %s %s %s"
 		     (cond
 		      ((equal org-babel-c-variant 'c) org-babel-C-compiler)
-		      ((equal org-babel-c-variant 'cpp) org-babel-c++-compiler))
+		      ((equal org-babel-c-variant 'cpp) org-babel-C++-compiler))
 		     (org-babel-process-file-name tmp-bin-file)
 		     (mapconcat 'identity
 				(if (listp flags) flags (list flags)) " ")