Add target_ops argument to to_get_trace_state_variable_value

Add target_ops argument to to_get_trace_state_variable_value

2014-02-19  Tom Tromey  <tromey@redhat.com>

	* tracepoint.c (tfile_get_trace_state_variable_value): Add 'self'
	argument.
	* target.h (struct target_ops)
	<to_get_trace_state_variable_value>: Add argument.
	(target_get_trace_state_variable_value): Add argument.
	* target.c (update_current_target): Update.
	* remote.c (remote_get_trace_state_variable_value): Add 'self'
	argument.
	* ctf.c (ctf_get_trace_state_variable_value): Add 'self' argument.