ARM: Fix generation of older veneers

[Christophe LYON]

Hi Daniel,

> This caused changes to the order of veneers (I do not really
> understand why, but I've had this problem before).  It also

stub offset are computed via bfd_hash_traverse, so I guess the 
hash_table is filled differently after your patch, leading to a 
different order of veneers. But why only such a small subset of the 
tests are impacted, I don't know.


> Any comments on this patch?
> 

For the change in arm_allocate_glue_section_space, maybe I would have 
move the BFD_ASSERT calls upper, so as to avoid checks against NULL in 
the case size==0; I think it would be easier to read, but it's probably 
a matter of taste.

It looks OK for me.

Christophe.