RFR: 8215412: Optimize PrintStream.println methods

[Claes Redestad]

Hi,

new webrev:

  http://cr.openjdk.java.net/~redestad/8215412/jdk.02/

- Adds a forgotten String.valueOf in println(String), making sure all
methods are semantically the same for
- Remove the isInternal method and use only exact match with
PrintStream.class to determine whether to use the optimized paths.

As before:

On 2018-12-14 21:22, Claes Redestad wrote:
> Same performance characteristics in the simple tests I've used to
> verify this, and no measurable regression (but no speed-up) for classes
> overriding PrintStream.

I've withdrawn the related CSR, since it's not relevant for this
implementation as it doesn't observably alter behavior of types
inheriting from PrintStream.

Thanks!

/Claes