All of the pre created nether portals in all of my world were no longer lit or only had 1 or 2 squares of portal.

Put the summary of the bug you're having here

What I expected to happen was...:
My portals to all be lit.
What actually happened was...:
my portals were unlit or there was only 1 or 2 blocks of portal left.

Steps to Reproduce:
1. Look at portals that were lit before you installed the snapshot.