* WFP rations cut by 20 percent due to funding shortfall
* Only $1.1 billion of $2.3 billion pledged to U.N. received
* Nearly half of all Syrians now displaced by conflict
By Stephanie Nebehay
GENEVA, April 7 (Reuters) - The United Nations has been forced to cut the size of food parcels for those left hungry by Syria's civil war by a fifth because of a shortage of funds from donors, a ...