complex can now be used as an identifier

Remove final vestiges of 'complex' keyword.

Closes #252

Examples/test-suite/not_c_keywords.i

@@ -0,0 +1,13 @@
+%module not_c_keywords
+
+%extend ComplexStruct {
+void init() {
+  $self->complex = 123;
+}
+}
+
+%inline %{
+struct ComplexStruct {
+  int complex; /* complex as variable name */
+};
+%}