Update llvm-lib to 6.0

Author: lembergerth

lib/ivy.xml

@@ -110,7 +110,7 @@
         <!--<dependency org="com.google.auto.value" name="auto-value" rev="1.3" conf="build->default"/>-->
 
         <!-- Shared C library for LLVM, bound by Java bindings -->
-        <dependency org="org.sosy_lab" name="llvm-lib-3.9.1" rev="3.9.1-sosy0.4" conf="runtime->full" />
+        <dependency org="org.sosy_lab" name="llvm-lib-6.0" rev="6.0-sosy0.6" conf="runtime->full" />
 
         <!-- Guava has a dependency on error_prone_annotations without a revision number, need an override. -->
         <override org="com.google.errorprone" module="error_prone_annotations" rev="2.4.0"/>