Workaround to fix PPComposedTest>>testLeftRecursion - make PPStream>>size returning size of the input.
For whatever reason, in Smalltalk/X ReadStream>>size returns size remaning data, not
the size of a whole stream. This is a bug and should be fixed in Smalltalk/X libbasic. Meanwhile,
override PPStream>>size to return proper value. In Pharo, the method is not needed as the inherited
method is exactly the same.