Remove pending_destroy_click variable.

Event bubbling on a destroy choice click stopped with #1142 which
means the pending destroy click never gets set to false which means
that the pending_destroy_click is unecessary.

Fixes #706
Merge branch 'master' into fix-delete-last-element-requires-two-clicks

Conflicts:
	chosen/chosen.jquery.js
	chosen/chosen.jquery.min.js
	chosen/chosen.proto.js
	chosen/chosen.proto.min.js
Merge pull request #1149 from harvesthq/fix-delete-last-element-requires-two-clicks

Remove pending_destroy_click variable.