search-again in frame:searchable<%>
Searches for the text in the search edit in the result of
get-text-to-search.
(-> booleansenda-frame:searchablesearch-againdirectionbeep?)
direction=previous searching direction:'forwardor'backward
beep?=#t: boolReturns
#tif the text is found and sets the selection to the found text. If the text is not found it returns#f.