TwentyTwelve: wp_title should be filtered

[DrewAPicture]

Per ​Best Practices, we should now be setting the example by properly filtering wp_title() instead of tacking on get_bloginfo('name') inside the <title> tags.

Patch attached.

[DrewAPicture]

If the conditions would be considered overkill, by all means chop away :)

[SergeyBiryukov]

#21233

[lancewillett]

In [21394]:

Twenty Twelve: better comment block for twentytwelve_wp_title() and set passed arguments to empty strings for compatibility with plugins or child themes that might override wp_title() before this filter runs.

See #21264.

[nacin]

In [21395]:

Revert parameter changes in [21394] as these are unnecessary.

Our plugin API always passes the requested number arguments to a callback,
even if previous callbacks asked for less arguments than later callbacks.

see #21264.