Fix string typemap when including std_string *after* other typemaps

Author: sethrj

Examples/test-suite/fortran_ownership.i

@@ -76,3 +76,18 @@ void do_nothing(TemplTricky<int>) {};
 %}
 
 %template(TemplTrickyInt) myns::TemplTricky<int>;
+
+// Test autofree declaration *before* including std:string
+%fortran_autofree_rvalue(std::string)
+namespace std {
+class string {
+};
+}
+
+%include <std_string.i>
+
+%inline %{
+std::string str_value(std::string s) { return s; }
+const std::string& str_cref(const std::string& s) { return s; }
+std::string& str_ref(std::string& s) { return s; }
+%}

Lib/fortran/std_string.i

@@ -32,6 +32,7 @@ class string;
 
 /* ---- CONST REFERENCE: NATIVE STRING ---- */
 
+%clear const std::string &;
 %typemap(ctype) const std::string & = char*;
 %typemap(imtype) const std::string & = char*;
 %typemap(ftype) const std::string & = char*;
@@ -57,6 +58,7 @@ class string;
 
 /* ---- VALUE: NATIVE STRING ---- */
 
+%clear std::string;
 %apply const std::string & { std::string };
 
 %typemap(globalin) std::string {