Roll Observatory packages and add a roll script

packages/petitparser/lib/petitparser.dart

Index: packages/petitparser/lib/petitparser.dart
diff --git a/packages/petitparser/lib/petitparser.dart b/packages/petitparser/lib/petitparser.dart
new file mode 100644
index 0000000000000000000000000000000000000000..5f559c95168117f17c9de69cfb154c661d3bea70
--- /dev/null
+++ b/packages/petitparser/lib/petitparser.dart
@@ -0,0 +1,16 @@
+/// This package contains the core library of PetitParser, a dynamic parser
+/// combinator framework.
+library petitparser;
+
+part 'src/petitparser/actions.dart';
+part 'src/petitparser/characters.dart';
+part 'src/petitparser/combinators.dart';
+part 'src/petitparser/composite.dart';
+part 'src/petitparser/context.dart';
+part 'src/petitparser/definition.dart';
+part 'src/petitparser/expression.dart';
+part 'src/petitparser/parser.dart';
+part 'src/petitparser/parsers.dart';
+part 'src/petitparser/predicates.dart';
+part 'src/petitparser/repeaters.dart';
+part 'src/petitparser/token.dart';