"Number of completion candidates below which cycling is used.
Depending on this setting `completion-in-region' may use cycling,
whereby invoking a completion command several times in a row
-completes to each of the candidates in turn, in cyclic manner.
+completes to each of the candidates in turn, in a cyclic manner.
If nil, cycling is never used.
If t, cycling is always used.
If an integer, cycling is used so long as there are not more