Warn when running the compiler under Java 6 or 7

(cherry picked from commit 5537800)

(cherry picked from commit 5614874)

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/CommonCompilerArguments.java

@@ -79,6 +79,9 @@ public abstract class CommonCompilerArguments implements Serializable {
     @Argument(value = "Xno-check-impl", description = "Do not check presence of 'impl' modifier in multi-platform projects")
     public boolean noCheckImpl;
 
+    @Argument(value = "Xskip-java-check", description = "Do not warn when running the compiler under Java 6 or 7")
+    public boolean noJavaVersionWarning;
+
     @Argument(value = "Xcoroutines=warn")
     public boolean coroutinesWarn;