#593 Allow annotations on events

• Best to review per commit.
• Code generator has some changes, similar to adding annotations on other kinds of objects:
  • doc annotations are added on declarations for C89/C99/Simulink, and on execution functions/methods for all targets.
  • No more post-comments for event declarations for C89/C99/Simulink.
  • Quoted event names for event declarations and event names lists for C89/C99/Simulink.

Addresses #593