RFR 8209138: Symbol constructor uses u1 as the element type of its name argument

[Harold David Seigel]

Hi,

Please review this change for bug JDK-8209138.  The fix changes class 
Symbol in symbol.hpp to use type char instead of types u1 and jbyte and 
renames relevant functions by replacing 'byte' with 'char'.  For 
example, 'Symbol::byte_at_put()' is now 'Symbol::char_at_put()'.

Open Webrev: 
http://cr.openjdk.java.net/~hseigel/bug_8209138/webrev/index.html

JBS Bug:  https://bugs.openjdk.java.net/browse/JDK-8209138

The change was tested by running Mach5 tiers 1 and 2 tests and builds on 
Linux-x64, Windows, and Mac OS X, running tiers 3-5 tests on Linux-x64, 
and by running JCK-11 API, Lang and VM tests on Linux-x64.

Thanks, Harold