Adds vdso to the module list at init time. Previously, it would be added upon execution (via the module event trigger), but would otherwise be absent.
I'd like to also add vsyscall, when it's separate, but it has no ELF header and that complicates placing it on the module list, so for now we leave it off.
Adds a release note as this could affect existing clients.
Tweaks drcovlib to handle displaced tags such as for the vsyscall hook.