cmd/heapview: add an internal core package for reading cores

This is based on github.com/tombergan/goheapdump/heapdump.

This CL mostly just copies over the 'raw' data structures based
on the profiler records' data structures. Many of them may need
to be changed, but I think it will be good to have these definitions
here to provide a base.

Change-Id: I609202b6b87d980b0835c8087b3d78e11bd6dfe3
Reviewed-on: https://go-review.googlesource.com/25584
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
2 files changed