Fix region length calculations when regions end with .align padding.

Fix region length calculations when regions end with .align padding.
* config/tc-ia64.c (output_endp): New.
(count_bits): Delete.
(ia64_flush_insns, process_one_record, optimize_unw_records): Handle
endp unwind records.
(fixup_unw_records): Handle endp unwind records.  Delete code for
shortening prologue regions not followed by a body record.
(dot_endp): Call add_unwind_entry to emit endp unwind record.
* config/tc-ia64.h (unw_record_type): Add endp.