[Bug fortran/62044] [4.8/4.9 Regression] ICE in USE statement with RENAME for extended derived type

[mikael at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62044

--- Comment #9 from Mikael Morin <mikael at gcc dot gnu.org> ---
Created attachment 34571
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34571&action=edit
segregate derived type namespaces from regular namespaces

To convince yourself that sym_root fields are never used in derived type
namespaces, here is a patch that gives a type without sym_root field to
f2k_derived.  It passes bootstrapping.