fixes ber decoding with longer certs

[manavk-p]

Allows for longer certs, such as some AWS certs, to be decoded properly. Taken from fullsailor#17

[manavk-p]

@ jvehent
This PR pulls in a change from a PR to fullsailor's repo. It allows for longer certs to be decoded without error.

[bernata]

@g-k there are still some issues with this PR; the go.mod in particular and i think it would be useful to have a real cert that demonstrates the need for this fix. If I fix those two issues [or more if you have them], do you feel it would be ok to merge?

[g-k]

@bernata Yes, I can take look, but I won't get to it until at least the end of the month.

Can you open a new PR with:

• a fixed go.mod
• a test with a real cert ideally from a well known service
• fullsailor@d25ebd6 cherry picked from upstream
• if applicable, tests from this branch 632789f (but not the merge back into master db74de8)

Thanks!

[g-k]

Superseded by #61