new style rule: misleading matrices

[florianschanda]

a = [1, 2, 3,
    4, 5, 6,
    8, 9, 10]

Is not the same as

a = [1, 2, 3, ...
    4, 5, 6, ...
    8, 9, 10]

We should maybe warn about the first one.

We should also consider a warning on:

a = [1, 2, 3; ... 
    4, 5, 6; ...
    8, 9, 10]