RFR: JDK-8219788: Configure recommends JDK 8

[Erik Joelsson]

Configure tries to be helpful with suggested commands for installing 
missing dependencies. The commands for installing a bootjdk are out of 
date and because of the accelerated release cycle, don't really work 
anymore. This patch changes the help text printed when the bootjdk is 
missing to "OpenJDK distributions are available at 
http://jdk.java.net/."; and removes all the OS specific help texts for 
that particular dependency.

Bug: https://bugs.openjdk.java.net/browse/JDK-8219788 
<https://bugs.openjdk.java.net/browse/JDK-8219788?filter=36357>

Webrev: http://cr.openjdk.java.net/~erikj/8219788/webrev.01/

/Erik