Fix undefined cl-macrorepxand-all under Emacs 24.4

Compilation is failing under Emacs 24.4 with the following error:

    Symbol's function definition is void: cl-macroexpand-all

The problem appears to be due to Emacs bug #18845[1]. The gist of
which is that cc-mode uses cl at compile time, but doesn't require
it. Requiring cl at compile time seems to fix it.

Fixes #9.

[1] <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18845>

Author: bookest

arduino-mode.el

@@ -32,6 +32,7 @@
 (require 'cc-mode)
 
 (eval-when-compile
+  (require 'cl)
   (require 'cc-langs)
   (require 'cc-fonts)
   (require 'cc-menus))