Single word correction (Zl) can fail without &wrapscan

[KSR-Yasuda]

How to repro

Run Zl at the pos below:

CORSS.CORSS
      ^

It happens if

• &wrapscan is disabled (set nowrapscan)
• The wrong words appear more than once in the buffer
• Cursor is on the beginning of the last word

Why this happens

In single word correction in spelunker#words#replace_word(),
it does /SERCHWORD/, N (move to previous word), and change the target word.

With &wrapscan (successful case),
it does /SEARCHWORD/ to move the next word, and comes back to the target word by N.

Without &wrapscan (bad case),
since the target word is the last appearance in the buf,
the /SEARCHWORD/ command fails, and cursor keeps its position.
So, if the cursor is on the beggining of the word,
the following N command jumps to the word before the target unexpectedly.

To fix this instantly, set &wrapscan in the operation.