* Assad seen more secure after military victories
* Warplanes hit Douma, 20 killed
* Government, opposition blame each other for gas attack
By Mariam Karouny
BEIRUT, April 13 (Reuters) - President Bashar al-Assad said on Sunday that Syria's three-year conflict was at a "turning point" due to his forces' military gains against rebels, state media said.
Assad's allies have ...