RFC: 8224599: Remove globals_ext.hpp

[Stefan Karlsson]

Hi all,

Is anyone using globals_ext.hpp? If not, I propose that we remove it and 
clean up the code using it.

http://cr.openjdk.java.net/~stefank/8224599/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8224599

Since globals_ext.hpp pulled in jvmFlag.hpp, I had to fix some includes 
and forward declarations.

Thanks,
StefanK