Add convention about patch names, which was discussed many times,
but no consensus was done.

PLEASE NOTE:

• This rule is valid for all *NEW* patches, which committers will add into the ports.

• It does *NOT* affect old patches which are still in the tree. So please do *NOT* change existing patch names just for new convention.

• Change patch names *ONLY* if you modify content of the patch.

Discussed with: linimon
Checked by: simon