[foreign] jextract does not filter typedefs, enums, and structs

[Jorn Vernee]

Hello,

Now that I'm done with the initial Windows support I have started 
looking for interesting Windows APIs to create tests/demos with. Pretty 
much any part of the Windows API requires users to include Windows.h, 
which is a huge header that pretty much includes everything and 
currently requires 14GB of RAM to extract. Trying to jextract a 
sub-header breaks the pre-processor code in those headers.

So, I'm using `--include-symbols` to select just the things I need, but 
I find TreeFilter [1] lacks filtering of typedefs, structs, and enums. 
So a lot of unneeded classes are still being generated. Why are these 
Tree types not currently filtered?

Thanks,
Jorn

[1] : 
http://hg.openjdk.java.net/panama/dev/file/d7885ab60131/src/jdk.jextract/share/classes/com/sun/tools/jextract/TreeFilter.java