vla: Fix check for vla used by autoconf

vla: Fix check for vla used by autoconf

1) recursive types have no storage anymore, so a
     static int (*p)[x];
   declaration is just fine
2) since somewhen VT_VLA doesn't imply VT_ARRAY anymore, so we
   now need to check VLA in at least one place before checking
   test_lvalue.

((2) should probably be cleaned up again so that VLA does again imply
ARRAY)