540156: Upgrade to Xtext 2.16 for 2018-12

Change-Id: I4d03c4ef9060362ee49bb542095c58d3359b7e75
Task-Url: https://bugs.eclipse.org/bugs/show_bug.cgi?id=540156
Signed-off-by: Lorenzo Bettini <lorenzo.bettini@gmail.com>
26 files changed