Remaining identifier macro issues

[dpk]

• (chibi syntax-case) still tries to import make-variable-transformer from (chibi) rather than (chibi ast) (this is my fault for forgetting that module still depends on make-variable-transformer even though identifier-syntax is gone from it!)

• identifier-syntax is still broken since the change to syntax-rules in 4382b9d:

  (import (chibi ast))
  (define-syntax foo (identifier-syntax (_ 'ref) ((set! _ _) 'set)))
  foo ;=> ERROR: cdr: not a pair: foo
  (foo) ;=> ERROR: non procedure application: ref (this is correct, but the next line isn’t)
  (foo x y) ;=> set

[dpk]

Also, make test-all still doesn’t include tests/syntax-tests.scm, which would have caught the second problem clearly.