gdbserver/linux-low: turn 'get_syscall_trapinfo' into a method

gdbserver/linux-low: turn 'get_syscall_trapinfo' into a method

gdbserver/ChangeLog:
2020-04-02  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	Turn the 'get_syscall_trapinfo' linux target op into a method
	of process_stratum_target.

	* linux-low.h (struct linux_target_ops): Remove the op.
	(class linux_process_target) <get_syscall_trapinfo>
	<gdb_catch_this_syscall>
	<low_supports_catch_syscall>
	<low_get_syscall_trapinfo>: Declare.
	* linux-low.cc (get_syscall_trapinfo): Turn into...
	(linux_process_target::get_syscall_trapinfo): ...this.
	(linux_process_target::low_get_syscall_trapinfo): Define.
	(gdb_catch_this_syscall_p): Turn into...
	(linux_process_target::gdb_catch_this_syscall): ...this.
	(linux_process_target::low_supports_catch_syscall): Define.

	Update the callers below.

	(linux_process_target::wait_1)
	(linux_process_target::supports_catch_syscall)

	* linux-x86-low.cc (class x86_target) <low_supports_catch_syscall>
	<low_get_syscall_trapinfo>: Declare.
	(x86_target::low_supports_catch_syscall): Define.
	(x86_get_syscall_trapinfo): Turn into...
	(x86_target::low_get_syscall_trapinfo): ...this.
	(the_low_target): Remove the op field.
	* linux-aarch64-low.cc (class aarch64_target)
	<low_supports_catch_syscall>
	<low_get_syscall_trapinfo>: Declare.
	(aarch64_target::low_supports_catch_syscall): Define.
	(aarch64_get_syscall_trapinfo): Turn into...
	(aarch64_target::low_get_syscall_trapinfo): ...this.
	(the_low_target): Remove the op field.
	* linux-arm-low.cc (class arm_target) <low_supports_catch_syscall>
	<low_get_syscall_trapinfo>: Declare.
	(arm_target::low_supports_catch_syscall): Define.
	(arm_get_syscall_trapinfo): Turn into...
	(arm_target::low_get_syscall_trapinfo): ...this.
	(the_low_target): Remove the op field.
	* linux-ppc-low.cc (the_low_target): Remove the op field.
	* linux-s390-low.cc (the_low_target): Remove the op field.