More miscellaneous Qt fixes

[s-mcf]

All the other stuff I have deserves its own PR, so this is probably the last 'misc fixes' PR for a while.

This PR contains the following:

• Fix a crash that would occur if a user Alt+F4'd with a game running
• Size the window up to fit the game if it's smaller than the IR (the user can still scale the window up or down once the game launches if they so choose)
• Fix the About Qt menu item not actually doing anything
• Bring in keyboard shortcuts from the wx UI.

What I'm working on next in rough order:

• Save states
• Movies
• Config window
• TAS (might need some help with this as I'm not too familiar with what a good TAS setup looks like)

[JMC47]

@dolphin-emu-bot rebuild

[dolphin-emu-bot]

FifoCI detected that this change impacts graphical rendering. Here are the behavior differences detected by the system:

• line-width-test on dx-win-nv: failed to render

_{^{automated-fifoci-reporter}}

[s-mcf]

Is this an issue with FifoCI? Nothing here should affect rendering...

[BhaaLseN]

The EC2 instances were stuck for quite some time, so they seem to be a bit wonky now that they had some vacation.