RFR: 8218738: Remove dead code in Symbol and friends

[Lois Foltan]

Looks good.
Lois

On 2/11/2019 9:58 AM, Claes Redestad wrote:
> Hi,
>
> JDK-8218675 is removing the last use of Symbol::as_utf8_flexible_buffer.
> This patch removes it, along with a few other methods, declarations etc
> in the area which are also no longer in use.
>
> Webrev: http://cr.openjdk.java.net/~redestad/8218738/open.00/
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8218738
>
> Testing: tier1
>
> Thanks!
>
> /Claes