The attached patch addresses most of the checkdoc warnings for 
org-capture.
There are two remaining warnings (both the same):

> Disambiguate org-capture-mode by preceding w/ 
> function,command,variable,option or symbol.

I did not address these because checkdoc has recently been fixed 
to stop asking for disambiguation of mode names:

http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=79a9b50621ec22640358bd6b94b65d14d747c644