[9] Review request for 8157002: Toggle gtk version if SWT used via FXCanvas

[Semyon Sadetsky]

Hello Kevin & David,

Please review the fix for jfx9:

bug: https://bugs.openjdk.java.net/browse/JDK-8157002

webrev: http://cr.openjdk.java.net/~ssadetsky/8157002/webrev.00/

In JFX embeded into SWT scenarios JFX loads GTK primarily. So SWT GTK 
version cannot be detected using the check for the loaded native library 
version.

The fix proposes a way to detect if GTK version of swt.jar library is 
available on the classpath and tries to get the GTK version from SWT lib 
internal java classes.

--Semyon