rtems-4.6ng11/powerpc: add updated stdint.h, disable strict aliasing in newlib

- newlib: add stdint.h, inttypes.h, update machine/types.h from 1.20.0
- newlib: build newlib with -fno-strict-aliasing, library code is
  not ready for strict aliasing
- newlib: enable -Wall and -Wextra warnings during build
- gcc: do not use __cxa_atexit() by default, newlib-1.11.0 does not
  provide it