Ada 2005 features

I am using GPS GPL 3.0.0 on windows XP and I try to play with some Ada
2005 features. Surprisingly when a try to compile the following minimal
test program (!):

package Test is
     
   type Cell is record
      Next : access Cell;
   end record;
   
end Test; 	

with the -gnat05 option I get the error

"type declaration cannot refer to itself"

When I try a compilation in Ada95 mode, I get

"generalized use of anonymous access type is an Ada 2005 extension"
"unit must be compiled with -gnat05 switch"

Are all the Ada2005 features really implemented in this version or are
there some of them still in project and in this case how can we get a
list of what is supported or not?

Thanks

Philippe Tarroux