Triage yara for Jessie.

Add link to fixing commit. The affected code is not present in Jessie. However
features to mitigate maliciously compiled bytecode were introduced only in later
versions. That means that this specific exploit might not work but there are
certainly other ways to escape the virtual machine if someone crafts a specific
rules file. It is not trivial to craft the file and to trick a security researcher
into using it. Hence this is no-dsa for Jessie.