Fixed scope of moved symbol

Because symbol was declared in outer scope it was being reused after being moved.
In practice this was not causing problems, but to avoid headaches it is better to move it to the loop scope so that it is reinitialised before being reused after being moved.

Author: NathanJPhillips

src/util/fresh_symbol.cpp

@@ -38,11 +38,10 @@ symbolt &get_fresh_aux_symbol(
   const irep_idt &symbol_mode,
   symbol_tablet &symbol_table)
 {
-  auxiliary_symbolt new_symbol;
-
   // Loop until find a name that doesn't clash with a non-auxilliary symbol
   while(true)
   {
+    auxiliary_symbolt new_symbol;
     // Distinguish local variables with the same name
     new_symbol.base_name=
       basename_prefix+"$"+std::to_string(++temporary_counter);