Merge changes I0feda6b2,I22d13fde,I49d7d09d,Ice490bfe into lmp-mr1-dev

* changes:
  Fix the type of u_ar0 in <sys/user.h>.
  Add greg_t for arm64.
  POSIX says <signal.h> gets you ucontext_t.
  Add in_port_t and move it and in_addr_t to the correct header file.