► The Problem:I use some third-party files in my WordPress plugin (or theme). When I run Poedit to built language files, it scans the main plugin folder and puts all text strings found in the .po file, including those from the third-party.
► The Solution?Vaclav Slavik, the author of Poedit, placed a "wontfix" resolution on that, years ago. See http://www.poedit.net/trac/ticket/359 and http://www.poedit.net/trac/ticket/253.
So, there is no official solution to this.
► So, what to do?Separate the 3rd party files from yours.
For example, put all your .php files into the "includes" folder, and 3rd party files - into the "vendor" folder. Then, in Poedit -> Catalog -> Properties -> Sources paths tab, instead of the "." (current folder), write "includes".
Poedit will scan only the "includes" and will ignore the "vendor" folder.