Merge Flycheck test suite into a single file

Loading all those test files took too long, and navigating them was a
hassle anyway.
Kill messages in reverse order

The kill ring is a stack, so we must reverse the order to have the first
message first in kill ring.
Add test for flycheck-copy-messages-as-kill
Remove superfluous mocker arguments

Min/Max occur defaults to 1 anyway.
Add test for flycheck-google-messages
Fix ordering of customize options
Fix version information with Emacs trunk

Emacs trunk has a refactored package.el with a different API.