[PATCH] Process record: Log %rax after syscall under amd64-linux

[Andrew D'Addesio]

Ah, I should have searched the bugzilla, as there's already a bug
report for this problem from 2016-06-25 by dev.burbrink:

    <https://sourceware.org/bugzilla/show_bug.cgi?id=20300>

So maybe it would be a good idea to add PR20300 to the commit message
and ChangeLog.

Andrew