Fix directorout typemaps which were causing undefined behaviour when returning pointers by reference.

Closes #1167

Lib/d/dswigtype.swg

@@ -185,7 +185,9 @@
 %typemap(directorin) SWIGTYPE *const&
   "$input = (void *) $1;"
 %typemap(directorout, warning=SWIGWARN_TYPEMAP_DIRECTOROUT_PTR_MSG) SWIGTYPE *const&
-  "$result = ($1_ltype)&$input;"
+%{ static $*1_ltype swig_temp;
+   swig_temp = ($*1_ltype)$input;
+   $result = &swig_temp; %}
 %typemap(ddirectorin,
   nativepointer="cast($dtype)$winput"
 ) SWIGTYPE *const& "($winput is null) ? null : new $*dclassname($winput, false)"