I looked at MPLAB 8.00 on one of my machines and the P16F1939.inc is not there. I skipped 8.15...
I checked for the file 16f1939.inc
I will assume that was in the PBP directory.
Goto - program files - microchip - MPASAM suite- and look for P16F1939.inc

But again I have not had a problem with old code moving forward with the exception of having a label named something that is now a reserved word (LOOP for example).