refactor: split variables declaration in test

[zielint0]

I am ready to merge.

[monperrus]

also explicitly initialize them to 0?

[zielint0]

@monperrus
No. Instead of adding 2 redundant initializers, I removed 1 redundant initializer. So the class is now:

class Counter {
			int scan;
			int enter;
			int exit;
		}

Class' fields have default initialization to 0 (or: "", null) so adding redundant initializer is redundant and confusing. Developer may wonder: why this initializer is added here, if this value is overrided by JVM?

Also it is confusing to trick user by override initializer later:

int x = 0;
... // some non x-activity
x = 2;

I removed such things here: https://github.com/INRIA/spoon/pull/2263/files

Please note that with removing such initializers, I removed other mistakes here. So some analysis paid off ;-)