Adds two events to trace syscalls in syscall emulation mode (*-user):
* guest_user_syscall: Emitted before the syscall is emulated; contains
the syscall number and arguments.
* guest_user_syscall_ret: Emitted after the syscall is emulated;
contains the syscall number and return value.
Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Message-id: 146651712411.12388.10024905980452504938.stgit@fimbulvetr.bsc.es
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>