`mem_size' and `init_phase'.
* fhandler_mem.cc (init): New function to figure out the size of
the physical memory.
(open): Add checking for illegal flags. Change usage of access mode.
(write): Add intended functionality.
(read): Add parameter checking. Eliminate page size constant. Use
getpagesize() instead. Don't touch errno and don't create debug output
while init() is running.
(lseek): Add bounds checking. Fix SEEK_END.
(fstat): Eliminate page size constant. Use getpagesize() instead.
(dup): Add intended functionality.