So far a lot of submitted PR have added symbols into the first
section. Split the file into `-released` and `-devel` to make
this more obvious.
To further enforce things, we hardcode a checksum of the `-released`
file in `test-symbols.sh`. Only release commits should update that
checksum.
Did you notice I like checksums?
Closes: #931
Approved by: pwithnall
Colin Walters