Fix for #33 and #27

Not sure if there was more you needed to do. For #27, the following slides didn't really mention the previous slides in detail, so I just swapped the pictures and think that's it.

For #33, I changed the basic "Hello World" to print "Hello World" three times, which allows the use of a for loop. Using this, I was able to illustrate the point that before C99 you couldn't declare the iterating variable within the `for`-statement (didn't mention C99 or C89). I put it here because you also illustrated the point that you can't use `\\` in "pure C" in this section as well, so I thought it fit.