The attached patch renames the extras directory to support, as 
suggested.  It also replaces test-skeleton.c with a thin wrapper around 
the new test driver.  I converted a few obscure tests (I remember one 
had its on static function forward declaration …), but compatibility 
should be pretty good now.

Build time before the patch:

real    0m55.779s
user    6m40.568s
sys     16m34.161s

Test time before the patch:

real    8m55.529s
user    43m59.488s
sys     21m53.491s

Build time after the patch:

real    0m55.924s
user    6m40.488s
sys     16m43.924s

Test time after the patch:

real    8m47.100s
user    43m11.433s
sys     21m57.057s

The system is completely unloaded otherwise.  The sys times vary quit a 
bit, but the wall clock time is stable.  In any case, there is no 
drastic change.

I had to rename the new test skeleton to <support/test-driver.c> because 
some existing tests use <test-skeleton.c> to refer to it, and this path 
got mapped to the new test skeleton (when it still had the old name), 
and not the old one with the compatibility hooks built in.

Thanks,
Florian