Use uint64 for BitBoard mask arrays
Vala is starting to check the size of a given integer constants and uses the appropriate type for it. See vala!273 (merged)
This leads to assignment errors which show implicit integer overflows.
../../../src/gnome3/gnome-chess/lib/chess-bitboard.vala:32.69-32.86: error: Expected initializer of type `int64' but got `uint64'
32 | 0x1000000000000000, 0x2000000000000000, 0x4000000000000000, 0x8000000000000000
| ^~~~~~~~~~~~~~~~~~