btrace: async support

Add support for async command execution.  This fixes the gdb.btrace tests.

	* record-btrace.c: Include event-loop.h and inf-loop.h.
	(record_btrace_resume_exec_dir)
	(record_btrace_async_inferior_event_handler)
	(record_btrace_handle_async_inferior_event): New.
	(record_btrace_open): Create async event handler.
	(record_btrace_close): Delete async event handler.
	(record_btrace_resume): Set record_btrace_resume_exec_dir,
	Mark async event handler.
	(record_btrace_execution_direction): New.
	(init_record_btrace_ops): Initialize to_execution_direction.
* guile/scm-type.c (type_smob): Remove duplicate typedef.
bfd/elfnn-aarch64.c: Cleanup a couple of TLS functions

Add an assert and remove an unused line of code.

bfd/ChangeLog:

2014-06-04  Will Newton  <will.newton@linaro.org>

        * elfnn-aarch64.c (tpoff_base): Make test of tls_sec
	being non-NULL into an assert.
	(elfNN_aarch64_tls_relax): Remove unused code.