Opinion of the Commission pursuant to Article 251 (2) (c) of the EC Treaty, on the European Parliament's amendments to the Council's common position regarding the proposal for a Directive of the European Parliament and of the Council relating to heating systems for motor vehicles and their trailers, amending Council Directive 1970/156/EEC and repealing Council Directive 1978/548/EEC - amending the proposal of the Commission pursuant to Article 250 (2) of the EC Treaty