Platform-specific default dimensions are unreachable

[stblr]

These platform-specific default dimensions are unreachable
https://github.com/tomaka/winit/blob/1b74822cfc0cb7fba4ed4940a3faae9499fcda95/src/platform/linux/x11/window.rs#L85-L87
https://github.com/tomaka/winit/blob/1b74822cfc0cb7fba4ed4940a3faae9499fcda95/src/platform/linux/wayland/window.rs#L27-L29
https://github.com/tomaka/winit/blob/1b74822cfc0cb7fba4ed4940a3faae9499fcda95/src/platform/windows/window.rs#L855-L857
https://github.com/tomaka/winit/blob/1b74822cfc0cb7fba4ed4940a3faae9499fcda95/src/platform/macos/window.rs#L758-L760
because dimensions is always Some.
https://github.com/tomaka/winit/blob/1b74822cfc0cb7fba4ed4940a3faae9499fcda95/src/window.rs#L147-L155

[francesca64]

This doesn't seem like such a bad problem? The platform-specific values don't really have any special meaning, so it's probably better to be uniform. (Though I'll admit it's confusing as-is)

@vberger I'm surprised I let that Wayland code pass review... what's up with 64x64?

[elinorbgr]

Hmm, looks like something I've set up for testing and forgot about, this should definitely not have been merged.

[madsmtm]

The default window size was removed in #1013, so I'll close this.