Postgres 9.2 - postgres - FATAL: XX000: relation mapping file "global/pg_filenode.map" contains incorrect checksum
Before I did anything, I would make a copy of the cluster as is and keep it safe, following the directions here: 

https://wiki.postgresql.org/wiki/Corruption 

Once you have your master copy safe, you might try a fresh initdb in another directory, and copy over the pg_filenode.map file, as suggested here, and see if that helps start your database:

http://tapoueh.org/blog/2013/09/16-PostgreSQL-data-recovery

If that doesn't work, or you encounter more errors, I would try pgsql-general@postgresql.org for more suggestions, or engaging a PostgreSQL consultancy to try and recover your data.

If it does work, I would do a pg_dump immediately, then initdb a new cluster on the new machine, and reload the pg_dump, just to make sure there isn't anything else lurking that could cause problems.

My sympathies on your issue, and best of luck getting it resolved.