Fix use-after-free in number_or_range_parser

-fsanitize=address showed a use-after-free in number_or_range_parser.

The cause was that handle_line_of_input could stash the input into
"saved_command_line", and then this could be freed by reentrant calls.

This fixes the bug by preventing commands that are read by "commands"
from being eligible for repeating.

gdb/ChangeLog
2018-08-17  Tom Tromey  <tom@tromey.com>

	* cli/cli-script.c (read_next_line): Pass 0 as repeat argument to
	command_line_input.

gdb/cli/cli-script.c

@@ -903,7 +903,7 @@ read_next_line (void)
   else
     prompt_ptr = NULL;
 
-  return command_line_input (prompt_ptr, from_tty, "commands");
+  return command_line_input (prompt_ptr, 0, "commands");
 }
 
 /* Return true if CMD's name is NAME.  */