Saudi Aramco boosting market share as it prepares for listing - CEO

* Energy sector will be "bridge to the long-term" - CEO * Saudi diversification plan "isn't saying no to oil" * Aramco market share up in 2015, 2016 - Nasser * IPO is at "the heart of Vision 2030" plan By Reem Shamseddine KHOBAR, Saudi Arabia, May 26 (Reuters) - Saudi oil giant Aramco is gaining market share and pushing for greater efficiency, chief executive Amin Nasser said in an interview, as it acts as a "bridge" to a future when the nation relies less on energy exports. Nasser also told Reu