<AWT Dev> RFR: 8154269: Remove unused or unnecessary Xm/Xt files and header includes

[Phil Race]

https://bugs.openjdk.java.net/browse/JDK-8154269
http://cr.openjdk.java.net/~prr/8154269/

https://bugs.openjdk.java.net/browse/JDK-8047931
listed a number of X11 and medialib files that are unused in the build.
In looking at the VDrawingArea ones it lead to realising
we still include Intrinsic.h (an Xt header) in awt.h even though
we do not use Xt since the Motif toolkit was removed.
So I think we can remove the dependency on those header files.
Doing this lead in turn to finding we have at least one unused
field, one unused #define and one unused method declaration
all referencing Xt types.

So I decided to separate out the removal of Xt headers and files in to 
this separate
bug report and make the other bug exclusively about medialib.

The fix adds into awt.h a couple of X11 includes that were implicit from
previously including Intrinsic.h and I explicitly added typedefs for Boolean
and Pixel which we were referencing in our code since those came from 
Intrinsic.h
I could perhaps have just changed the one usage of Pixel to "unsigned long"
but Boolean was used more widely.

JPRT has passed builds on all platforms and JDK still seems to work fine 
on Linux ..

One other note : awt_InputMethod.c has a number of places where it
still mentions OSX. I didn't attempt to clean that up here as I suspect
it would muddy the patch.

   93 #if defined(__linux__) || defined(MACOSX)



-phil.