This has been working since at least Linux Mint 13 and is confirmed to work on the latest Linux Mint 18 Sarah/Cinnamon.
- Locate the libhunspell 1.3 (or whatever) library: locate libhunspell-1.3
- go there
- link to the old library name sudo ln -s libhunspell-1.3.so.0 libhunspell-1.2.so.0
- restart rssowl
Don’t ask me why this hasn’t been fixed in the software yet as it’s many years old.