[GNC] Data format compatibility between recent versions

[John Pastore]

I reviewed FAQ section 3.3, but it does not cover more recent versions of
Gnucash.

I use Gnucash 3.1 on Windows (7) and Gnucash 2.6.12 on Linux (Ubuntu 16.04
LTS), soon to transition to 2.6.19 on Ubuntu 18.04 LTS.

Data file portability appears to be fine in both directions, but I just
want to make sure there are no specific cases that might result in data
file corruption.

Any advice much appreciated!

John