fixed low hanging fruit

[mcrossen]

This fixes quite a few compiler warnings. A lot of them were improper use of the format string in printf functions... which is actually a security risk (https://stackoverflow.com/questions/7459630/how-can-a-format-string-vulnerability-be-exploited)

[mcrossen]

don't merge this quite yet, I just saw something I need to fix

[plusk01]

@mcrossen thanks for all your work on this!

I didn't change any of the original code because I didn't want to unknowingly introduce any differences in the assembler output or in the overall behavior of the system (i.e., for grading). What do you think?

[mcrossen]

@plusk01 That's a good point. As of today, your repo is the official 425 source (see the class webpage), so its smart to be careful about what gets added.
Perhaps the best thing would be to create a 'development' branch for those students who know what they're doing and want to use a better version. Alternatively, you could release the code as it is now, so that students could access the vanilla code. I kinda think the 'development' branch is the most effective method in this case.
btw, I made that fix I mentioned in a previous comment. this PR is good to go.