Update HP-UX readme

The porting center cannot be said to ship recent perl when 5.18.0 is about
to be released and they just have 5.10.1 available. Trying "very hard" now
sounds like a huge overstatement. Sadly.

Telling what modules were included in the first public perl port from HP is
like digging up corpses.

HP-UX 11.31 has now EOL set to 2022. I've updated all other EOL info too.