Remove "repeat" argument from command_line_input

Remove "repeat" argument from command_line_input

After the previous patch, all callers pass 0 as the repeat argument to
command_line_input.  So, this patch removes it.

gdb/ChangeLog
2018-08-16  Tom Tromey  <tom@tromey.com>

	* top.c (read_command_file): Update.
	(command_line_input): Remove "repeat" argument.
	* ada-lang.c (get_selections): Update.
	* linespec.c (decode_line_2): Update.
	* defs.h (command_line_input): Remove argument.
	* cli/cli-script.c (read_next_line): Update.
	* python/py-gdb-readline.c: Update.