Do this to reduce conflicts with <linux/input.h>, which contains some
conflicting defines.
This changes the meaning of MP_KEY_DOWN:
KEY_DOWN is renamed to MP_KEY_DOWN (cursor down key)
MP_KEY_DOWN is renamed to MP_KEY_STATE_DOWN (modifier for key down state)
This commit makes `is_osx_version_at_least` cache the result of reading
`/System/Library/CoreServices/SystemVersion.plist`. Since that is a file
read operation it was bad to use this function frequently (i.e.: when
processing user events).
Remove `is_lion_or_above` (introduced in c9396c0a) as that was a more
specialized wrapper which had the only advantage of adding it's own cache.
Gestalt is deprecated since 10.8. Change the code to read the OS version from
a system plist file.
As mentioned http://stackoverflow.com/a/11072974/499456 Apple engineers are
suggesting this plist reading approach.