[Bug fortran/85407] Replace gcc_assert in module.c:read_module by more helpful diagnostics

[kargl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85407

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4
            Version|unknown                     |9.0
           Assignee|unassigned at gcc dot gnu.org      |kargl at gcc dot gnu.org
   Target Milestone|---                         |9.0