Add PTRACE_GET_SYSCALL_INFO from Linux 5.3 to sys/ptrace.h.

Linux 5.3 adds a PTRACE_GET_SYSCALL_INFO constant, with an associated
structure and PTRACE_SYSCALL_INFO_* constants.

This patch adds these to sys/ptrace.h in glibc
(PTRACE_GET_SYSCALL_INFO in each architecture version, the rest in
bits/ptrace-shared.h).  As with previous such constants and associated
structures, the glibc version of the structure is named struct
__ptrace_syscall_info.

Tested for x86_64, and with build-many-glibcs.py.