Re-add interface of SRFI-42, which was accidentally removed on the last commit.

scheme/more-interfaces.scm

@@ -648,3 +648,23 @@
    option-optional-arg?
    option-processor
    args-fold))
+
+(define-interface srfi-42-interface
+  (export ((do-ec
+	    list-ec append-ec
+	    string-ec string-append-ec
+	    vector-ec vector-of-length-ec
+	    sum-ec product-ec
+	    min-ec max-ec
+	    any?-ec every?-ec
+	    first-ec last-ec
+	    fold-ec fold3-ec) :syntax)
+	  ((:
+	    :list :string :vector
+	    :integers
+	    :range :real-range :char-range
+	    :port
+	    :dispatched) :syntax)
+	  ((:do :let :parallel :while :until) :syntax)
+	  :-dispatch-ref :-dispatch-set! make-initial-:-dispatch 
+	  (:generator-proc :syntax)))