Add Clean Transparency feature

Only in the Cocoa dialog right now
Cocoa radio button tweak

Figured out how to track radio buttons properly in Cocoa, so spreading
the love. Not really necessary, but...
Added pngquant

Only added controls for the Cocoa dialog so far.
Setting pngquant speed

Also threw in a few PIUpdateProgress() and TestAbort calls for good
measure.
Enable dithering

Per pull request #1
Moved ADM headers to after __LP64__

Avoids problems when building under newer OS X SDKs.
Get rid of Carbon dependency in Cocoa dialog
Merge branch 'master' into clean_transparent
Merge branch 'clean_transparent' into pngquant
Tweak Xcode target settings
Use slider label to give feedback on the meaning of the setting
Reorder scripting params

Turns out the order we use to write these is reflected in the action
recorded.
Adding Quantize controls to ADM dialog

For 32-bit on OS X
Encourage higher qualities
Add Quantize to Windows

Because pngquant relies heavily of C99, must build this with Visual
Studio 2013. Even then, I have to use the "msvc" branch of pngquant.
Merge pull request #4 from pornel/qualities

Encourage higher qualities
Turn on SSE on Windows in pngquant

OpenMP currently has some issues, so I'm leaving it off.
Changed to Kornel's quality labels
Update ADM dialog with Kornel's labels
Add Kornel's name to the About dialogs

These things could really look a lot better.