Move Scilab Travis testing from trusty to xenial

.travis.yml

@@ -285,7 +285,7 @@ matrix:
       os: linux
       env: SWIGLANG=scilab
       sudo: required
-      dist: trusty
+      dist: xenial
     - compiler: gcc
       os: linux
       env: SWIGLANG=tcl

Tools/travis-linux-install.sh

@@ -114,6 +114,10 @@ case "$SWIGLANG" in
 		fi
 		;;
 	"scilab")
+		# Travis has the wrong version of Java pre-installed resulting in error using scilab:
+		# /usr/bin/scilab-bin: error while loading shared libraries: libjava.so: cannot open shared object file: No such file or directory
+		echo "JAVA_HOME was set to $JAVA_HOME"
+		unset JAVA_HOME
 		travis_retry sudo apt-get -qq install scilab
 		;;
 	"tcl")