Twenty Thirteen: Update calendar widget styles for 5.4 markup

[sabernhardt]

Since the previous month and next month links are no longer inside table cells in version 5.4, display:block stretches each of those links the full width of the calendar container.

Though I like how the month links are larger and further away from the calendar date links, the change would be quite unexpected for other people.

(markup was changed for ticket:39763)

[sabernhardt]

comparing side widget in 5.3 and 5.4

[sabernhardt]

comparing footer widget in 5.3 and 5.4 (at narrow width so they are aligned in one column instead of using masonry)

[sabernhardt]

Using display:table to nearly match the former styles

[sabernhardt]

Using display:inline-block for the new span elements

[sabernhardt]

comparing patches for side widget next to 5.3 styles

[sabernhardt]

comparing patches for footer widget (again, in one column) next to 5.3 styles

[sabernhardt]

Option 1: 49546.patch

• Uses display:table and display:table-cell to nearly match the former styles (the .pad in between the links is slightly narrower)
• Reinstates the line-height of 2 for the navigation links
• Moves the table's bottom margin to the nav element

Option 2: 49546.1.patch

• Simply adds display:inline-block to the new span elements (it may be preferable to add that to the .wp-calendar-nav span a elements instead)