Restrict the name used in %extend to be just the struct/class name and not a typedef to a class/struct. Typedefs were only partially working anyway. Anonymous struct typedefs excluded. Deprecate with a warning for now.

Examples/test-suite/errors/swig_extend.i

@@ -0,0 +1,35 @@
+%module xxx
+
+typedef struct {
+  int myint;
+} StructA;
+
+typedef struct StructBName {
+  int myint;
+} StructB;
+
+typedef struct StructC {
+  int myint;
+} StructC;
+
+%extend StructA {
+  void method() {}
+}
+
+%extend StructB {
+  void method() {}
+}
+
+%extend StructC {
+  void method() {}
+}
+
+struct StructD {
+  int myint;
+};
+typedef struct StructD StructDName;
+
+%extend StructDName {
+  void method() {}
+}
+