It's better to signal an error on R7RS syntax-rules when it couldn't build output

[Takashi Kato]

This type of macro should raise an error the same as R6RS.

(import (scheme base))
(define-syntax zipm
  (syntax-rules ()
    ((_ (x ...) (y ...))
     (list '(x y) ...))))
(zipm (1 2 3) (1 2 3 4))

[Takashi Kato]

Adding input form length check on multiple template variable expansion. (Fixes #151)

→ <<cset be5c7085411e>>