Use function stub behaviour in single-function mode

Previously function stubs were only applied when static-analysis
was called against a goto_functions object; they are now applied
when it is called against a goto_programt as well.

Author: smowton

src/analyses/static_analysis.cpp

@@ -509,8 +509,16 @@ void static_analysis_baset::do_function_call_rec(
 {
   // see if we have the functions at all
   if(goto_functions.function_map.empty())
+  {
+    if(function.id()==ID_symbol)
+    {
+      auto fid=function.get(ID_identifier);
+      if(!should_enter_function(fid))
+        transform_function_stub(function.get(ID_identifier),new_state,l_call,l_return);
+    }
     return;
-
+  }
+  
   if(function.id()==ID_symbol)
   {
     const irep_idt &identifier=function.get(ID_identifier);