PRECIOUS-Gold firms above $1,900/oz as weaker yields bolster appeal

* Markets await U.S. GDP, jobs data * U.S. Treasury yields at two-week low (Recasts, adds comment, updates prices) By Arundhati Sarkar May 26 (Reuters) – Gold rose above the key $1,900 level for the first time since January on Wednesday, driven by a retreat in U.S. Treasury…