10 RFR (XS) 8193764: Cannot set COMPANY_NAME when configuring a build

[mark.reinhold at oracle.com]

Bug: https://bugs.openjdk.java.net/browse/JDK-8193764
Webrev: http://cr.openjdk.java.net/~mr/rev/8193764/

You can set COMPANY_NAME in make/autoconf/version-numbers, but you can't
set it when configuring a build, so it's impossible to change the value
of IMPLEMENTOR in the $JAVA_HOME/release file without patching the
source code.

This patch simply adds the obvious --with-vendor-name option to the
configure script.

(Motivation: I'm trying to arrange for IMPLEMENTOR to be "Oracle
 Corporation" in builds produced by Oracle, but this option may prove
 useful to other implementors.)

- Mark