This is the update for libreadline from 4.3 to 5.0, the update is rather painless and seems to work fine
on both 4.x and 5.x. One thing I noticed is that the patches are not on MASTER_SITE_GNU for readline-5.0
as they were for readline-4.3, to work around this I hardcoded the readline's master site to PATCH_SITES,
at least until they update the other sites.