Replace images in wxRendererMac::DrawTitleBarBitmap() with drawing code.

[TcT2k]

The low resolution (14x14) bitmaps scaled badly on high resolution displays. A close button suitable for usage inside a window (like wxInfoBar) is not available via HI theme drawing methods. This drawing code tries to emulate a close button, as close as possible to the one found in the Xcode 6+ welcome window.

Normal: Hover: Old implementation:

[TcT2k]

@vadz previous comments where lost when I pushed the updated implementation, so I'll reply here:
I wasn't even ware that GetContentScaleFactor() returns something on MSW. I've updated the second commit to include other ports too. It looks much better now on Windows. But a little bit of platform specific code is still required as only the OSX version of wxBitmap has ctors with a specifiable content scaling factor.

Windows 8.1 (200%):

[vadz]

This could be written a bit more clearly as Deflate(5*contentScale).

[vadz]

Sorry for the delay, I've finally reviewed the latest version of the patch. If the latest comments could be addressed (especially the one about CreateScaled()), I promise to apply this without any further delay. TIA!

[TcT2k]

I've integrated your comments, but I wasn't able to use wxBitmap::CreateScaled() (which is currently undocumented) as the result was an empty bitmap. I'm not really sure why as the code looks correct when stepping into it. It would obviously be cleaner without the #ifdef but I couldn't find a way to make it work without the cocoa specific ctor.

[vadz]

It would be great if somebody with a retina Mac could debug this, it's really appalling that we don't have a way to create a bitmap in a portable way :-(

Also, sorry to be a pain, but what about the hardcoded RGB values? They seem to be there without any explanations...

[TcT2k]

@vadz
I've misinterpreted CreateScaled. I thought it would create a scaled bitmap based and the current content, but obviously it creates the bitmap object like other Create methods.
The code now works without ifdefs. I've tested OS X and Win 8.1 with a 4K display and the results match the screenshots posted above.

As for the RGB values I've included a comment that they are hard coded based on the Xcode 6+ welcome screen. I haven't found a good match using any system colors, which would obviously be a nicer approach.

I've also added documentation for CreateScaledin an additional commit.

[vadz]

Great, thanks for fixing this!