Create inferior for ctf target.

Create inferior for ctf target.

This patch creates inferior when GDB opens a ctf trace data, to be
consistent with tfile target.  A test case is added to test for
live target, tfile and ctf target.

gdb:

2014-02-05  Yao Qi  <yao@codesourcery.com>

	* ctf.c: Include "inferior.h" and "gdbthread.h".
	(CTF_PID): A new macro.
	(ctf_open): Call inferior_appeared and add_thread_silent.
	(ctf_close): Call exit_inferior_silent and set inferior_ptid.
	(ctf_thread_alive): New function.
	(init_ctf_ops): Install ctf_thread_alive to to_thread_alive.

gdb/testsuite:

2014-02-05  Yao Qi  <yao@codesourcery.com>

	* gdb.trace/report.exp (use_collected_data): Test the output
	of "info threads" and "info inferiors".