Checked a solution to Homework 4, Problem 2 into the
repo. This includes the code appearing on the take-home final,
but is more complete. See file hw04-kernel-sol.cu.
Fixed a problem with the hw04 package that prevented cuda-gdb
from working properly. The fix modifies hw04.cc and Makefile.
Executiong git pull is safe if these files have not been
modified and should be safe if the lines around NPerf_init
in hw04.cc were not modified.