All map()-Methods could take FnMut-Closures as arguments

[StT191]

Currently all the map()-methods of the glam vector-types require the mapping function to implement Fn.
However they could all take a function with a more flexible FnMut requirement like the primitive array-types do in std.

Of course anybody who would need to map with a FnMut-closure could convert to/from array and use the array-map-method.
But being able to use the map()-methods of the glam-types would be much nicer in that case.

[bitshifter]

Done

[StT191]

Nice