Avoid name collisions on C code

[PalumboN]

• [ ] Avoid two functions with the same name -> remane. If both are <api> then throw an error.
• [ ] Same name in local variable names and functions. We can rename the local variables using _ prefix.

[PalumboN]

Right now:

• Having two methods blah and blah: (no-accessors of a struct) generates two functions with the same name -> Fail C compilation.
• Defining a method like:

algo
	| setupStack |
	setupStack := 6.
	self setupStack: 5.
	^ setupStack

Fails because local variable and message send are translated with the same name