TinyMCE: fix 3.x callbacks added with init.setup as they run before the...

TinyMCE: fix 3.x callbacks added with init.setup as they run before the compat3x plugin is loaded. Ideally this will be fixed internally in TinyMCE, see #24067.
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git-svn-id: https://core.svn.wordpress.org/trunk@26859 1a063a9b-81f0-0310-95a4-ce76da25c4cd