Change the deployment target and SDK.
Change the CFBundleExecutable variable in the plists to ${EXECUTABLE_NAME}. This is preprocessed to the correct value when the project is built.
Editing the Xcode project:
Get rid of a lot of old, useless, and/or bad build options.
Upgrade based on Xcode 4.6's options.
Include a missing plist in the Xcode project, and move the dangling one to its proper subfolder