Add support of internal arguments for language feature settings

Arguments are passed in form '-XXLanguage:+LanguageFeatureName' for enabling
LanguageFeature.LanguageFeatureName, and '-XXLanguage:-LanguageFeatureName'
for disabling.

Note that they do override other settings, including 'language-version'
or extra ('-X') args.

js/js.frontend/src/org/jetbrains/kotlin/js/config/ReleaseCoroutinesDisabledLanguageVersionSettings.java

@@ -25,6 +25,11 @@ public class ReleaseCoroutinesDisabledLanguageVersionSettings implements Languag
         return delegate.getFeatureSupport(feature);
     }
 
+    @Override
+    public boolean isPreRelease() {
+        return delegate.isPreRelease();
+    }
+
     @Override
     public <T> T getFlag(@NotNull AnalysisFlag<? extends T> flag) {
         return delegate.getFlag(flag);