[10] RFR: 8184665: Skip name and alias checks for standard Charsets

[Claes Redestad]

Hi,

by special-casing the three Charsets we always load on startup in the 
Charset
constructor we can avoid some superfluous checks and get a tiny startup
improvement (~7k less bytecode executed, which is fast approaching 1% of 
total
on minimal startup tests).
Webrev: http://cr.openjdk.java.net/~redestad/8184665/jdk.00/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8184665

Thanks!

/Claes