Fix program arguments (main.cc)

[rgsilva]

We all know that program arguments are really useful tools. But today I was messing with the main.cc and I've found 3 problems:

1) DRY (don't-repeat-yourself). The code "execute(); shutdown();" is repeated over and over. Should be a good idea to move it to the bottom? 2) The "-i" argument: it isn't documented and it doesn't work (at least as an interative mode). Probably because the current state is not being stored. 3) The "-p" argument: it's a debug one and should be mentioned on the usage information, when available.

[felipensp]

1) go for it 2) It must work, probably it's buggy now. Need to check. 3) go for it

Thanks.

[rgsilva]

2) As I told you before, the import is not working. For example:

[Ricardo@PIOS clever]$ clever -i
import std;
Int foo = 42;
println(foo);
Compile error: Function 'println' does not exists! on line 1
[Ricardo@PIOS clever]$

But if you import before the println, it works.

[Ricardo@PIOS clever]$ clever -i
Int foo = 42;
import std; println(foo);
42

[Ricardo@PIOS clever]$

But I'm gonna create an issue for this one, ok?