uBPF jitter is should have option to apply constant blinding

[Alan-Jowett]

uBPF jitter is should have option to apply constant blinding

Code generated by the uBPF jitter is susceptible to JIT spray attacks. See: https://www.usenix.org/sites/default/files/conference/protected-files/woot18_slides_gawlik.pdf

For a good description of the attack.

Proposed fix: https://samsung.github.io/kspp-study/bpf.html#hardening-hostile-code-in-ebpf

[rlane]

SGTM

[Alan-Jowett]

This is primarily needed when jitting code from untrusted sources. This and issue #73 are needed when loading code from untrusted users.