Changing native source file extensions from .mm to .cpp in preparation for Android build.
-Added Android support (requires the Android NDK)
-Changed some link types for the default lib to make Android ANE work.  Did not yet test this with iPad hardware!
-Updated required AIR SDK version to 3.9
-Got rid of bullet-ane Xcode workspace because the BulletANE Xcode project contains the required Bullet projects anyway.
-Simplified Bullet SVN checkout script
Updated the README
xcodebuild from command line wasn't working right, so I reverted to building the iOS part from the Xcode GUI.  This is reflected in the README.