Release coccinelle-0.2.1

Release coccinelle-0.2.1

** Language:
   - Add virtual identifiers
   - Add coccilib.report and coccilib.trac Python modules
   - coccilib.org and coccilib.report are imported by default but not loaded
     in the current scope.

** Features:
   - Parse_error_msg now more helpful.  New option -verbose_parsing for even
     more information.
   - Improve Python import handling. They are imported once during script
     initialization.

** Bugfix:
   - correct treatment of depends on with || for virtual rules