The import forms miss to match the keywords `only`, `prefix`, `rename`, ... by binding

[mnieper]

Chez Scheme defines an import form for local imports (see sections 10.4 and 11.6 in the CSUG). It defines auxiliary keywords like only, except or rename for use with import (see section 11.5 and https://github.com/cisco/ChezScheme/blob/main/s/syntax.ss#L7564). However, these bindings are useless because the keywords in import forms are matched by symbolic names (see, e.g. https://github.com/cisco/ChezScheme/blob/main/s/syntax.ss#L4150), which is contrary to the intuition and to the rest of the Scheme language where keywords (e.g. else) are matched by binding (i.e. free-identifier=?).

If there is agreement that this should be corrected, I can prepare and send a patch through a pull request.