Fixed flycheck workaround when completion is aborted(#300)

[kumar8600]

Thank you for issue reopening. I fixed behavior when completion is aborted.

Fixed points:

• I made to start flycheck's syntax checking when completion is aborted too.
  • I add timer to detect completion is aborted.
  • I add user customizable variable to custom above timer's polling interval.
• I made to load Flymake and Flycheck (if exist) before defadvice.
• I splited function ac-setup for ac-syntax-checker-workaround because it becomes long.

[syohex]

I merged.