(Adds Federer result) May 17 (Reuters) – Czech Tomas Berdych snapped a run of 11 consecutive defeats by world number one Novak Djokovic to reach the semi-finals of the Rome Masters before Rafa Nadal was stretched to the limit against David Ferrer on Friday. Berdych clawed his way back from a 6-2 5-2 deficit to stun the Serbian top seed 2-6 7-5 6-4 and set up a semi-final meeting with Nadal, who for the second week running outlasted compatriot Ferrer in a fierce claycourt scrap. …