RFR: JDK-8157336: Generation of classlists at build time should be configurable

[Erik Joelsson]

Generating a classlist at build time is not supported on all JVM 
configurations. This patch adds a configure flag to control this build 
step: --disable-generate-classlist. The default is to be enabled if 
either a client or server JVM Variant is being built.

Bug: https://bugs.openjdk.java.net/browse/JDK-8157336
Webrev: http://cr.openjdk.java.net/~erikj/8157336/webrev.top.01/index.html
/Erik