The previous hash was not unique for changes in integer/boolean values.
Generic hash_combine routines provide decent coverage for limited extra
cycles.
Therefore, for some footprints, the right footprint was not associated to the component.
The hash calculation was using a XOR to combine 2 sub hash values.
This is not a strong way to combine these hash values.
They are now added. Looks better to identify similar and different footprints.
Fixes: lp:1847575
https://bugs.launchpad.net/kicad/+bug/1847575
Seth Hillbrand
jean-pierre charras
Maciej Suminski