Some text files included in jfxrt.jar have GPL copyright

The source code files in the javafx repository include a GPL v2 + CLASSPATH license copyright header. In the Oracle JDK build some of these source files are included in the jfxrt.jar runtime with the original GPL license still in place. This is a mistake and needs to be corrected.

Note that an OpenJFX build must retain these copyright headers, so we will need conditional build logic to swap out the headers much as we do for creating the javafx-src.zip file.