My English is bad :-(
It is either trinary, or ternary, but not what I've written in previous 
message.
Thanks to Timur for pointing to this issue.
Here goes a new version of the patch with proper naming for an new option 
type. 
-- 
Nikolay Shaplov aka Nataraj
Fuzzing Engineer at Postgres Professional
Matrix IM: @dhyan:nataraj.su