Revert "libffi 3.0.12"

This reverts commit 2efe718a3b4b5e124004fdbb68cc13da5c8de41c.
libffi: note why we reverted
Adding libmodbus.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
libmodbus 3.0.3

Closes #18263.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
bash 4.2.45
wireshark 1.8.6