Add special variable imfuncname expansion for C# and D

Same functionality as Java

Doc/Manual/D.html

@@ -267,6 +267,12 @@ SomeClass bar() {
 </pre></div>
   </dd>
 
+  <dt><tt>$imfuncname</tt></dt>
+  <dd><p>
+This special variable expands to the name of the function in the intermediary class that will be used in $imcall.
+Like, $imcall, this special variable is only expanded in the "dout" typemap.
+  </p></dd>
+
   <dt><a name="D_importtype"></a><tt>$importtype(SomeDType)</tt></dt>
   <dd>
     <p>This macro is used in the <tt>dimports</tt> typemap if a dependency on another D type generated by SWIG is added by a custom typemap.</p>