Fix improper initialization order for readline.

Turns out we must set rl_basic_word_break_characters *before* we call
rl_initialize() the first time, because it will quietly copy that value
elsewhere --- but only on the first call.  (Love these undocumented
dependencies.)  I broke this yesterday in commit 2ec477dc8108339d;
like that commit, back-patch to all active branches.  Per report from
Pavel Stehule.

src/bin/psql/input.c

@@ -346,8 +346,10 @@ initializeInput(int flags)
 		char		home[MAXPGPATH];
 
 		useReadline = true;
-		rl_initialize();
+
+		/* these two things must be done in this order: */
 		initialize_readline();
+		rl_initialize();
 
 		useHistory = true;
 		using_history();