Making C tutorial better

The changes I made come in a few broad classes:

1) The style in the code wasn't great (mainly in the control statements).  A lot of bunched-up code in the if's and while's.  I went ahead and spread it out.
2) A lot of the comments were vague and not as precise as they could have been. I added a section about sizeof and beefed up the malloc conversation.
3) The original tutorial gave exact bit-sizes for ints, shorts, longs, etc.  Those bit sizes were generally incorrect (an int is not always 32 bits, etc.), so I went ahead and edited those sections to have more accurate information.