jdk7 incompatibility: red good code is green: always check signature erasure equals for jdk7 (IDEA-66311)

add checks for param erasure for jdk6

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting/IDEA66311.java

@@ -0,0 +1,21 @@
+import java.util.*;
+
+class ErasureTest {
+  <error descr="'toArrayDouble(List<? extends Number>)' clashes with 'toArrayDouble(List<double[]>)'; both methods have same erasure">public static double[] toArrayDouble(List<? extends Number> v)</error> {
+    return null;
+  }
+
+  public static double[][] toArrayDouble(List<double[]> v) {
+    return null;
+  }
+}
+
+class ErasureTest1 {
+  <error descr="'toArrayDouble(List<? extends Number>)' clashes with 'toArrayDouble(List)'; both methods have same erasure">public static double[] toArrayDouble(List<? extends Number> v)</error> {
+    return null;
+  }
+
+  public static double[][] toArrayDouble(List v) {
+    return null;
+  }
+}