Autosave:

- Move the 'Saving post' and 'Draft saved at...' strings from autosaveL10n to postL10n as they are used only there.
- Use the custom jQuery events 'before-autosave' and 'after-autosave' to show these messages.
- Separate autosave.suspend() for local and server so local autosaves can continue while server autosaves are suspended.
- Remove the recently added autosave.server.disable() and use autosave.server.suspend() instead.
- Bring back .button.disabled, button-primary.disabled and use .disabled to prevent multiple form submissions.
See #25272.

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git-svn-id: https://core.svn.wordpress.org/trunk@26914 1a063a9b-81f0-0310-95a4-ce76da25c4cd