Now that we have the necessary functions to deal with this in the
low-level HCL API, it's more intuitive to use bare identifiers for these
parameter names. This reinforces the idea that they are symbols being
defined rather than arbitrary string expressions.
This is a super-invasive update since the "zcl" package in particular
is referenced all over.
There are probably still a few zcl references hanging around in comments,
etc but this takes care of most of it.
The main "zcl" package requires a bit more care because of how many
callers it has and because of its two subpackages, so we'll take care
of that one separately.
This package provides helper function that looks in a given body for
blocks that define functions, returning a function map suitable for use
in a zcl.EvalContext.
