Add macro/function comment generation.

Add:
	vim/bundle/doxygen_utility/plugin/doxygen_utility.vim
		-Add `GenerateMacroComment()` and `GenerateFunctionComment()`, which
		extract the macro and function definition/declaration respectively
		from under the cursor and insert a `Doxygen` comment string with
		appropriate specifiers (`@param`, `@return`) depending on its content.
		-Prevent `IsOnFunction()` regex from ignoring `static` functions, which
		were erroneously excluded.