Fixes:
maps03.c: In function 'main':
maps03.c:15:32: error: result of '10l << 30' requires 35 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
  mem = (void *)mmap(NULL, (10L << 30), PROT_READ | PROT_WRITE,
                                ^~
maps03.c:22:9: error: result of '4l << 30' requires 34 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
  mem[4L << 30] = 1;
         ^~
maps03.c:23:9: error: result of '8l << 30' requires 35 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
  mem[8L << 30] = 2;
         ^~
maps03.c:30:13: error: result of '4l << 30' requires 34 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
  if (mem[4L << 30] != 1 || mem[8L << 30] != 2) {
             ^~
maps03.c:30:35: error: result of '8l << 30' requires 35 bits to represent, but 'long int' only has 32 bits [-Werror=shift-overflow=]
  if (mem[4L << 30] != 1 || mem[8L << 30] != 2) {
                                   ^~

Proceses virtual address space is smaller than 4Gb - omit this test for
those archs.
Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>