Twenty Twelve: make small-screen menu accessible to keyboard commands and voice-driven software by using a focusable button element rather than `h3` for the toggle element. Fixes #28224, props rclations.
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Twenty Fourteen: more graceful handling of super-long site titles in small screens: add an ellipsis and adjust `max-width` more carefully.

Props celloexpressions, schoenwaldnils, and obenland -- fixes #28237.
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git-svn-id: http://core.svn.wordpress.org/trunk@28882 1a063a9b-81f0-0310-95a4-ce76da25c4cd