lang/org: fix errors lazy-loading mismatched babel libraries

The ob-C.el library takes care of C, C++ and D. This modifies the babel
lazy-loader to take this into account. Name => library mappings are
defined in +org-babel-mode-alist.

modules/lang/org/+babel.el

@@ -2,6 +2,14 @@
 
 (add-hook 'org-load-hook #'+org|init-babel)
 
+(defvar +org-babel-mode-alist
+  '(("cpp" . C)
+    ("C++" . C)
+    ("D" . C)
+    ("matlab" . octave))
+  "An alist that maps languages to babel libraries. This is necessary for babel
+libraries (ob-*.el) that don't match the name of the language.")
+
 (defun +org|init-babel ()
   (setq org-src-fontify-natively t      ; make code pretty
         org-src-preserve-indentation t  ; use native major-mode indentation
@@ -13,8 +21,11 @@
     "Load babel libraries as needed when babel blocks are executed."
     (let* ((language (org-element-property :language (org-element-at-point)))
            (lang-sym (intern language)))
-      (unless (cdr (assoc lang-sym org-babel-load-languages))
-        (require (intern (format "ob-%s" language)))
+      (when (and (not (cdr (assq lang-sym org-babel-load-languages)))
+                 (require
+                  (intern (format "ob-%s"
+                                  (or (cdr (assoc (downcase language) +org-babel-mode-alist))
+                                      language)))))
         (add-to-list 'org-babel-load-languages (cons lang-sym t)))
       (apply orig-fn args)))
   (advice-add #'org-babel-execute-src-block :around #'+org*babel-execute-src-block)