Fix InnerAssignment check for lambda expressions.

Assignments statements in single statement lambda expressions are not
inner assignments.

Fixes #377.

src/main/java/com/puppycrawl/tools/checkstyle/checks/coding/InnerAssignmentCheck.java

@@ -59,6 +59,7 @@ public class InnerAssignmentCheck
             TokenTypes.RESOURCES,
             TokenTypes.RESOURCE_SPECIFICATION,
         },
+        {TokenTypes.EXPR, TokenTypes.LAMBDA},
     };
 
     /**