fix docs for `call-with-default-reading-parameterization'
raco pkg catalog-{show,copy}: add `--version' flag
pkg catalog protocol: document 'versions field
package system: clients extract version-specific info from a catalog result

When a client sends a query to a package catalog, it includes a
version number in the query, and a package catalog can customize its
response to the version. That approach allows evoluation of the way
that versions are mapped to results, but it does not allow a
directory-implemented catalog to offer version-specific information.
Allowing both the server and the client to filter on the version is
even more flexible, and in particular allows a directory-implemented
catalog to include version-specific mappings.
pkg/lib: add `pkg-directory->module-paths'
meta/pkg-push: add module and dependency information
fix some missing native-library dependencies
faster paths for parameter lookup

Calling a parameter function (with no arguments) can be 2-3 times
as fast as before.
setup/dirs: add `find-user-links-file'
fix immutable hash tree balancing

When an existing entry in the AVL tree for an immutable hash
is replaced with a new one, the new one did not always get
the right depth, which could throw off the tree balance.