[racket] Quasiquotation in (shared ...) form not documented

>From some simple tests, it appears that quasiquoted expressions are 
substituted properly within the (shared ...) form, such as in the 
following case:

(shared ((foo `(,foo bar))) foo)

This feature is not documented in the manual 
(http://docs.racket-lang.org/reference/shared.html); the only shell-expr 
forms listed there are things like cons and list.  Having quasiquotation 
in (shared ...) is convenient, and so I believe it should be documented.

-- Jeremiah Willcock