(vb_off_identifier): New variable to hold the identifier for the
sigtable field vb_off.
(init_decl_processing): Initialize vb_off_identifier.
Renamed vt_off_identifier from offset_identifier.
(init_decl_processing): Add vb_off field to sigtable_entry_type.
Reorder fields so that pfn gets properly aligned at a 64 bit boundary
on the Alpha.
(init_decl_processing): Align sigtable_entry_type on word
boundaries instead of double word boundaries to save space.

From-SVN: r10171