Update main.cu

Added const in computeHistogram declaration for consistency and added conditionals to be able to run it on Windows and/or Linux.
Merge pull request #7 from macias/patch-1

Update main.cu
Merge branch 'master' of github.com:udacity/cs344
adding HW6 files
Merge branch 'master' of https://github.com/udacity/cs344
adding missing student_func.cu file
Merge branch 'master' of github.com:udacity/cs344