LP conventions:
 
* When a macro introduces new variable identifiers which is available
in a "body" of the form, we surround the identifiers with parens, and
position them just before the body.  For example,
 
(sessioned-response (sesh req) body-goes-here-and-may-refer-to-sesh-and-req ...)
 
Here sesh and req are both identifiers (not expressions bound in the
enclosing environment.  The inspiration for this convention is lambda,
in which, in most cases at least, the first argument is a list of
identifiers.
 
* When a function takes a single xexpr we often use the identifier
  "body".  But if the function expects an arbitrary number of xexpr,
  then we encourage the use of the identifier "bodies".