Changes on floats

Floats ending with "." are deprecated in Scala 2.10, so there is no need
to support this syntax.
Some changes on identifiers

* infix operations starting with letters now also support the operator
  suffix (e.g. should_==)
* identifiers starting with keywords should no longer be confused with
  other productions (e.g. classOf is never the start of a class
  definition)