Fix unwind info problems with .align.

Fix unwind info problems with .align.
* config/tc-ia64.c (slot_index): New arg before_relax.  Use instead of
finalize_syms.
(fixup_unw_records): New arg before_relax.  Pass to slot_index.
(ia64_estimate_size_before_relax): New.
(ia64_convert_frag): Pass 0 to fixup_unw_records.  Add comment.
(generate_unwind_image): Pass 1 to fixup_unw_records.
* config/tc-ia64.h (ia64_estimate_size_before_relax): Declare.
(md_estimate_size_before_relax): Call ia64_estimate_size_before_relax.