Remove the "Change MAC Address" screen, and simply generate a new (random) one upon pressing the button.
Merge pull request #6518 from thedax/ui-rand-mac

Remove the "Change MAC Address" screen, and generate a random one instead.
Fix Win32 builds and remove the new MAC address editing prompt.
Merge pull request #6577 from thedax/win32-buildfix

Win32 buildfix. Remove the new MAC address editing prompt, too.