* module/language/c99/info.scm (clone): Add post field.
(make): Handle post parameter.
* module/language/c99/compiler.mes (clone): Handle post parameter.
(expr->accu*): Set it to support foo--/foo--.
(expr->accu): Read it to support foo--/foo--.
* scaffold/tests/7o-struct-pre-post.c: Test it.
* build-aux/check-mescc.sh: Run it.
