MFC r249238, r249239:

r249238:

Use 4-byte padding for core dump notes on both 32 and 64bit archs.

Although native word padding (i.e. 8-byte on 64bit arch) looks to be
in agreement with standards, other parts of our code and other OSes
use 4-byte alignment.

This is not expected to change alignment for currently generated core
dump notes, as the notes look to consist of structures with sizes
multiple of 8 on 64-bit archs. But there are plans to add additional
notes, where 4-byte vs 8-byte alignment makes difference.

Discussed with: kib
Reviewed by: kib

r249239:

Fill p_flags and p_align fields of the core dump note segement.

Reviewed by: kib