Fix two CSS issues in the 3.8 branch.

 * Comments dashboard widget: Use the proper class to avoid stretched "unapproved" red lines. [27564]
 * Fix the tags input in small viewports and make it a more reasonable size. (Was unusable in Firefox.) [27254]

fixes #26910, #27082.

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git-svn-id: http://core.svn.wordpress.org/branches/3.8@27708 1a063a9b-81f0-0310-95a4-ce76da25c4cd