[Pharo-project] PetitSmalltalk: portable number parsing

I've attached a fix to PetitParser, using Number class >> #readSmalltalkSyntaxFrom: instead of Number class >> #readFrom:. The former selector makes clear the intention of reading a Smalltalk number. The latter selector means something slightly different in at least one Smalltalk: in Squeak, Number class >> #readFrom: is more "user facing" in the sense that it accepts a range of number representations that are not valid syntax. This change has no impact for Pharo because it has this selector: http://code.google.com/p/pharo/issues/detail?id=2063 (thanks to Nicolas Cellier). This fix makes PetitSmalltalk's tests all pass in Squeak. frank