#746470 by follow-up by aspilicious, Jacine, jbrown, sgabe, et al: Add border-radius for IE9 / Opera 10.50

#544398 by Gábor Hojtsy, mr.baileys: Fixed Delete buttons look disabled in Seven theme even though they're not

#599706 follow-up by JohnAlbin, sun: Regression: Restore consistency to theme_menu_local_tasks() theme function

- Patch #896828 by Jeff Burnz, Manuel Garcia, yoroy, bleen18: no visual connection between the active tab and its content.

- Patch #896364 by frega, effulgentsia, Jacine, sun, David_Rothstein, Jeff Burnz, james.elliott, casey, mgifford: screen reader users and some keyboard only users need a clear, quick way to disable the overlay.

- Patch #639460 by Jeff Burnz, effulgentsia, Jacine, mgifford, james.elliott: evaluate CSS of #skip-link, .element-focusable, and upcoming 'disable overlay' links for their impact on contrib/custom themes.

#931682 follow-up by aspilicious, corbacho: Be more specific about which headings should not be bold in Seven.

- Patch #769226 by Owen Barton, sun, effulgentsia, alanburke, bleen18, mfer: optimize JS/CSS aggregation for front-end performance and DX.

#699858 by David_Rothstein, catch, yoroy, sun, ronald_istos, et al: Fix admin/by-task is confusing because it looks too similar to admin/config. Makes admin/by-task a very minimal view, and makes admin/by-module a more fully fledged index.

- Patch #896828 by Jeff Burnz, Manuel Garcia, yoroy: vertical tabs - no visual connection between the active tab and its content.

#882164 by aschiwi, Gábor Hojtsy, David_Rothstein, reglogge, et al: Fix the 'install from another language' instructions so that they actually work.