iOS failed to get platform type

[kotori2]

We should include "iOS" in ENG_getPlatform, but since header use pfif.getPlatform() as well, we might need change the platform api or check what official engine do.

function platform._init(this)
  if ENG_getPlatform():find("Win32") ~= nil then
  elseif ENG_getPlatform():find("iOS") ~= nil then
  else
  end
  this._platform_str, this._platform = ENG_getPlatform(), L1_1.ANDROID
  this._app_version = L2_2(is_function_type(ENG_getAppVersion) and ENG_getAppVersion() or "(none)")
  this._is_debug = not ENG_isRelease()
end