expression a new variable in the local module is defined in terms
of an equally named variable from some other module, use @ to
refer to the variable in the other module. This is necessary due
to section 5.2.1 of R5RS: In a define expression first the new
binding is created and then the expression is evaluated.
* srfi-17.scm: Mark replacements.
* boot-9.scm (module-make-local-var!): Use module-add!.
(module-primitive-add!): New function.
(resolve-interface): Use
(call-with-deferred-observers, module-call-observers): New
functions.
(module-defer-observers, module-defer-observers-mute,
module-defer-observers-table): New variables.
(process-define-module, process-use-modules, export, re-export):
Use call-with-deferred-observers.
* syncase.scm (eval): Mark as replacement.
* boot-9.scm (defmacro-public): Use export-syntax instead of export.
* srfi-19.scm, srfi-17.scm, srfi-16.scm, srfi-14.scm, srfi-13.scm,
srfi-11.scm, srfi-10.scm, srfi-9.scm, srfi-8.scm, srfi-6.scm,
srfi-2.scm: Use `cond-expand-provide' for providing features to
`cond-expand'.
