Symbols' owner are not always up to date

[smarter]

For example:

class Meter(val underlying: Int) extends AnyVal

class Test {
  val x: Int = new Meter(3).hashCode() 
}

new Meter(3).hashCode() should be replaced by Meter.hashCode$extension(3) in phase VCInline but it isn't because isMethodWithExtension returns false for hashCode because its owner is Any. This is incorrect because the phase SyntheticMethods will add an hashCode method to Meter. For value classes this problem can only happen with hashCode and equals (and a few other methods if the value class is also a case class), so I could work around it by hardcoding these methods into isMethodWithExtension, but maybe it's worth solving the underlying problem, I don't know what consequences it could have.

[DarkDimius]

Changes that should follow merging #515 should change how SyntheticMethods handles value classes.

SyntheticMethods already specially handles synthesis of every method for value class. After #515 gets merged, there would be less methods to synthesize and thus less special handling.