Masts are not always for communication

[sanderd17]

The tag man_made=mast only says something about the physical look of the structure, not it's function. See http://wiki.openstreetmap.org/wiki/Tag:man_made%3Dmast

Next to communications, it can also be used for lightening (of football stadions f.e.), or for sports like popinjay archery.

Currently, the icon communications.p.20.png is used for all man_made=mast objects, that icon has a visualisation of "broadcasting" next to the mast view.

According to the wiki, it's advised to add tower:type=communication if the mast is used for communication purposes.

So I propose to use a version without broadcasting for a simple man_made=mast, and a version with broadcasting when tower:type=communication is added.

I made a simple icon of a mast, based on the communications icon, but where I just coloured the broadcasting stuff away. I hope it's good enough.

[HolgerJeromin]

related to #339

[nebulon42]

I thought too that this needs upgrade, but it seems that tower:type is in the rendering database already (openstreetmap-carto.style#L137).