[binutils-gdb] Implement get_syscall_trapinfo for aarch64-linux

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 061fc021d5d110cc37a4c06c4ed94b87be00610a ***

Author: Yao Qi <yao.qi@linaro.org>
Branch: master
Commit: 061fc021d5d110cc37a4c06c4ed94b87be00610a

Implement get_syscall_trapinfo for aarch64-linux

gdb/gdbserver:

2016-06-28  Yao Qi  <yao.qi@linaro.org>

	* linux-aarch64-low.c (aarch64_get_syscall_trapinfo): New
	function.
	(the_low_target): Install aarch64_get_syscall_trapinfo.