Display language features warnings during compile

When compiling Scala scripts, display verbose warnings
when language features are used but not enabled.
This extra warning appears on the Gerrit log and allows
to better troubleshoot common problems.

Change-Id: I1ba9dff2262acc899e5c9a685a648da936f5d212

src/main/java/com/googlesource/gerrit/plugins/scripting/scala/ScalaSettings.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/scripting/scala/ScalaSettings.java b/src/main/java/com/googlesource/gerrit/plugins/scripting/scala/ScalaSettings.java
index 322cff1..3827397 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/scripting/scala/ScalaSettings.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/scripting/scala/ScalaSettings.java
@@ -37,6 +37,7 @@
     settings.exposeEmptyPackage().tryToSetFromPropertyValue("true");
     settings.Ylogcp().tryToSetFromPropertyValue(CLASSPATH_DEBUG);
     settings.verbose().tryToSetFromPropertyValue(VERBOSE_COMPILE_OUTPUT);
+    settings.feature().tryToSetFromPropertyValue("true");
 
     settings.outputDirs().setSingleOutput(initVirtualDirectory());
     settings.classpath().tryToSetFromPropertyValue(