Support catch syscall on aarch64 linux

Support catch syscall on aarch64 linux

Hi,
This patch is to support catch syscall on aarch64 linux.  We
implement gdbarch method get_syscall_number for aarch64-linux,
and add aarch64-linux.xml file, which looks straightforward, however
the changes to test case doesn't.

First of all, we enable catch-syscall.exp on aarch64-linux target,
but skip the multi_arch testing on current stage.  I plan to touch
multi arch debugging on aarch64-linux later.

Then, when I run catch-syscall.exp on aarch64-linux, gcc errors that
SYS_pipe isn't defined.  We find that aarch64 kernel only has pipe2
syscall and libc already convert pipe to pipe2.  As a result, I change
catch-syscall.c to use SYS_pipe if it is defined, otherwise use
SYS_pipe2 instead.  The vector all_syscalls in catch-syscall.exp can't
be pre-determined, so I add a new proc setup_all_syscalls to fill it,
according to the availability of SYS_pipe.

Regression tested on {x86_64, aarch64}-linux x {native, gdbserver}.

gdb:

2015-03-18  Yao Qi  <yao.qi@linaro.org>

	PR tdep/18107
	* aarch64-linux-tdep.c: Include xml-syscall.h
	(aarch64_linux_get_syscall_number): New function.
	(aarch64_linux_init_abi): Call
	set_gdbarch_get_syscall_number.
	* syscalls/aarch64-linux.xml: New file.

gdb/testsuite:

2015-03-18  Yao Qi  <yao.qi@linaro.org>

	PR tdep/18107
	* gdb.base/catch-syscall.c [!SYS_pipe] (pipe2_syscall): New
	variable.
	* gdb.base/catch-syscall.exp: Don't skip it on
	aarch64*-*-linux* target.  Remove elements in all_syscalls.
	(test_catch_syscall_multi_arch): Skip it on aarch64*-linux*
	target.
	(setup_all_syscalls): New proc.