DOSBox GUI update

An update for the DOSBox configuration GUI. This time, it's starting to look a little more like the Windows 95 interface rather than Windows 3.1. This looks a little less retro, but leaves more space for the window contents. Check out the screenshot below.

Changes:

• Added X close button
• Autoexec editor now has scrollbars
• Cosmetic changes resulting in smaller dialogs (or the same size with extra space)
• Dropdown for full-screen resolution setting
• Fixed combobox and system menu not being closed when clicking the activating control again
• Fixed help text for "speed"
• Fixed memory leak (actually, 2 of em: also check this post)
• Fixed text wrapping when moving window off the right of the screen

Remaining known issues:

• Issues with OpenGL as mentioned before, especially with full-screen mode — the issues themselves aren't unique to the GUI, but also exist in the keymapper
• The "execute now" button in the autoexec editor leaves a spurious prompt/li>

Here's a new screenshot so you can see what it looks like in the new Windows 95 look: