fix/expand/improve docs on "config.rktd"

Merge to v6.0
make installers: install required packages, first

This change should fix a problem with the Mac OS X PPC build,
where the "libsqlite3" shared library needs to be installed
early. The same strategy is already used for Windows.

Merge to v6.0
define-runtime-path: add support for version search to 'so form

Merge to v6.0