Roll Observatory packages and add a roll script

packages/petitparser/lib/src/lisp/standard.dart

-part of lisp;
+part of petitparser.lisp;
 
-/**
- * The standard library.
- */
+/// The standard library.
 class Standard {
 
-  /** Imports the standard library into the [environment]. */
+  /// Imports the standard library into the [environment].
   static Environment import(Environment environment) {
     evalString(lispParser, environment, _standardLibrary);
     return environment;
   }
 
-  /** A simple standard library, should be moved to external file. */
+  /// A simple standard library, should be moved to external file.
   static String _standardLibrary = """
 ; null functions
 (define null '())
 (define (null? x) (= '() x))
 
 ; booleans
 (define true (and))
 (define false (or))
 
 ; list functions
@@ skipping 34 matching lines @@
 
 (define (inject list value proc)
   (if (null? list)
     value
     (inject
       (cdr list)
       (proc value (car list))
       proc)))
 """;
 }