Makefile: add simple makefile for UNIX systems
main.c: more understandable usage string
main.c: better message when the file does not exist
main.c: AFAIK exit(1) is more common than exit(-1)
main.c: paragraphs nazism

I guess you know what I mean.
main.c: wrap long line in a reasonable way
main.c: wrap another long line
main.c: consistent indent
Makefile: be more general and invoke cc
Add a simple program that may overflow
Merge pull request #1 from bassosimone/master

Set of simple, mainly-cosmetic changes