(sieve-parse-command): Bugfix: must always return a list whose car is

the token type.
New command line options: --debug and --lib-dir

@@ -318,7 +318,7 @@
    ((eof-object? current-token)
     (syntax-error "Expected string-list but found " current-token))
    ((eq? (car current-token) 'string)
-    (list (cdr current-token)))
+    (list 'string-list (cdr current-token)))
    ((not (eq? (car current-token) 'delimiter))
     (syntax-error "Expected string-list but found " (car current-token)))
    ((char=? (cdr current-token) #\[)
@@ -876,8 +876,13 @@
 (define output #f)
 
 (define (sieve-usage)
-  (display "usage: sieve.scm --file FILENAME [--output FILENAME]")
-  (newline)
+  (display "usage: sieve.scm [OPTIONS]\n")
+  (display "GNU sieve.scm -- compile a Sieve program into Scheme code\n")
+  (display "Options are:\n")
+  (display "   -f, --file FILENAME      Set input file name\n")
+  (display "   -o, --output FILENAME    Set output file name\n")
+  (display "   -L, --lib-dir DIRNAME    Set sieve library directory name\n")
+  (display "   -d, --debug LEVEL        Set debugging level\n")
   (exit 0))
 
 (define (sieve-expand-filename name)
@@ -907,6 +912,10 @@
             (value #t))
     (output (single-char #\o)
 	    (value #t))
+    (debug  (single-char #\d)
+	    (value #t))
+    (lib-dir (single-char #\L)
+	     (value #t))
     (help   (single-char #\h))))
 
 (define program-name (car (command-line)))
@@ -916,8 +925,12 @@
    (cond
     ((pair? x)
      (case (car x)
+       ((debug)
+	(set! sieve-debug (string->number (cdr x))))
        ((file)
 	(set! filename (cdr x)))
+       ((lib-dir)
+	(set! sieve-libdir (cdr x)))
        ((output)
 	(set! output (cdr x)))
        ((help)