Its root cause is a difference between the "readline" and "libedit" (header files)
definitions of "rl_completion_entry_function", where the "libedit" one is wrong anyway:
This variable is used as a pointer to a function returning "char *",
but "libedit" declares it as returning "int" and then adds casts on usage.

Change it to "CPFunction *" and get rid of the casts.


client/mysql.cc:
  Fix bug#23293 "readline detection broken on NetBSD":
  
  Now that the "libedit" header files declares "rl_completion_entry_function" correctly,
  it need not be cast on usage, and "no_completion()" can be declared to return "char *".
cmd-line-utils/libedit/readline.c:
  Fix bug#23293 "readline detection broken on NetBSD":
  
  Now that the "libedit" header files declares "rl_completion_entry_function" correctly,
  it need not be cast on usage, and "complet_func()" is a "CPFunction *" as well.
cmd-line-utils/libedit/readline/readline.h:
  Fix bug#23293 "readline detection broken on NetBSD":
  
  Declare "rl_completion_entry_function()" to be a "CPFunction *", this avoids casts
  and brings "libedit" in sync with "readline".