Test Program for Safecopy with or without COW

How to run
==========

Test safecopy with COW:
  1. Set USE_COW_SAFECOPY to 1 in /usr/src/kernel/system/do_safecopy.c
  2. Type `make run` to prepare and run test.
  3. When done testing, type `make clean` to clean up.

Test safecopy without COW:
  1. Set USE_COW_SAFECOPY to 0 in /usr/src/kernel/system/do_safecopy.c
  2. Type `make run` to prepare and run test.
  3. When done testing, type `make clean` to clean up.

If you want to modify the test buffer size:
  1. Modify TEST_PAGE_NUM in inc.h
  2. Modify TEST_PAGE_SHIFT in inc.h