Search query should be urlencoded in get_search_feed_link() and get_search_comments_feed_link()

[tenpura]

get_search_feed_link() and get_search_comments_feed_link() do not urlencod the search query properly.

They return URLs like

http://example.com/?s=あ い&feed=rss2

which should be like

http://example.com/?s=%E3%81%82+%E3%81%84&feed=rss2

[tenpura]

urlencode search query

[azaozz]

(In [12395]) Urlencode the search query in get_search_feed_link() and get_search_comments_feed_link(), props tenpura, fixes #11153