Mac debug libs package has wrong/misleading "welcome" text

The four mac debug libs packages (e.g. qt-mac-cocoa-opensource-4.6.2-debug-libs.dmg) present the same Welcome message as the regular mac packages. This has lead at least one user to (erroneously) conclude that they only need to download the debug-libs package – see QTBUG-10231.

The debug-libs packages should have different Welcome text that clearly tells the user that they need to have installed the regular package first, and correctly states what is contained in the debug-libs package.