wp_widget_rss_output() cleanup

[SergeyBiryukov]

There are some issues in wp_widget_rss_output():

• […] is never appended to $summary since [27691] (see lines 876 and 881).
• wp_html_excerpt() can cut a string in a middle of a word. wp_trim_words() should be used instead, which would make some of the other string manipulations here redundant.
• $title is escaped with esc_attr(), but never used as an attribute. esc_html() should be used instead.

[SergeyBiryukov]

28356.patch​ fixes these issues and also includes UmeshSingla's 26552.patch:ticket:26552​.

[SergeyBiryukov]

In 28586:

Clean up wp_widget_rss_output():

• Fix appending […] to $summary.
• Use wp_trim_words() instead of wp_html_excerpt().
• Trim $title before checking if it's empty. props UmeshSingla.
• Use correct escaping function for $title.

fixes #28356.