Try both old and new buffer protocols on python2.7

While some objects on 2.7 might only implement the old buffer protocol,
some (notably memoryview) only implement the new buffer protocol, so
both need to be tried.

src/wxpybuffer.h

@@ -31,8 +31,9 @@ class wxPyBuffer
         #if PY_MAJOR_VERSION < 3
             // Old buffer protocol
             int rv = PyObject_AsReadBuffer(obj, (const void**)&m_ptr, &m_len);
-            return rv != -1;
-        #else
+            if (rv != -1)
+                return true;
+        #endif
             // New buffer protocol
             Py_buffer view;
             if (PyObject_GetBuffer(obj, &view, PyBUF_SIMPLE) != 0)
@@ -41,7 +42,6 @@ class wxPyBuffer
             m_len = view.len;
             PyBuffer_Release(&view);
             return true;
-        #endif
     }