SDL*Window: Verify that we get an accelerated ctxt

This is supposed to weed out "bad" graphics drivers that SDL somehow
picks up if we request an MSAA level higher than what the better driver
supports - namely the "GDI Generic" driver under Windows.

Also verify that we actually get a backbuffer with the requested number
of MSAA samples for the same reason.
Move config queries out of SDL*Window
Window: Allow changing the title

Also remove title param from initialize() and instead allow setting
the title before that.
[style] Rename Window::position_ to m_position
[style] Rename Window::size_ to m_size
[style] Rename Window::isMinimized_ to m_minimized
[style] Rename Window::isMaximized_ to m_maximized
[style] Rename Window::isVisible_ to m_visible
[style] Rename Window::isFullscreen_ to m_fulls...