segfault in translate_common()

[Paul Thomas]

Bernhard,

> The patch below fixes your problem but "perturbs" my fix for module 
> equivalences; the test cases work perfectly but the module 
> equivalences to common variables manage to be associated with 
> different external symbols, which are none the less correctly aligned! 
> I obviously need to understand this before emitting a patch and a test 
> case.  Otherwise it regtests on FC3/Athlon.

Bother, I tell a lie -  FAIL: gfortran.fortran-torture/execute/common_2.f90

I really will have to go through the logic with a fine tooth comb.  
Nearly there!

Paul T