Use this function before set_search_text, to unescape the following sequences of characters: `\n`, `\r`, `\t` and `\\`.
The purpose is to easily write those characters in a search entry.
Note that unescaping the search text is not needed for regular expression searches.
See also: escape_search_text.
| text |
the text to unescape. |
|
the unescaped |