The SmalltalkScanner used for refactorings, live error reporting and some
other IDE purposes, loses the sign of simple negative floats. This hasn't
mattered much to date because the literal values generated are not consumed,
e.g. when an AST is used to reformat code, the original number syntax is
preserved.

To Reproduce evaluate:

(SmalltalkScanner on: '-1.23' readStream) next value "=> 1.23"

Obviously the result should be -1.23.

1-line fix and test value update in 8. For 7.1, ported over most of the
ScannerTest class from 8.

Too dependent on network config of the host