.osx: Add back the “increase window resize speed” hack

It didn’t work in OS X 10.10 anymore, but it seems OS X 10.10.1 does support it.

Ref. 4471e2732faede1d9b242cb547de8005578b3d10.
Merge commit '7197c5739d7b54b6476dd0c54d9e34d41a42bdfd'

* commit '7197c5739d7b54b6476dd0c54d9e34d41a42bdfd':
  .osx: Add back the “increase window resize speed” hack