system.h and system header include cleanup

[Laurynas Biveinis]

2010/11/27 Joseph S. Myers <joseph@codesourcery.com>:
>        * ggc-zone.c: Don't include <sys/mman.h>.
>        (MAP_ANONYMOUS, MAP_FAILED): Don't define.

ggc-zone.c is not compiled unless configured with --with-gc=zone, so
would you mind doing 'make ggc-zone.o' to make sure it still builds OK
with the change?

-- 
Laurynas