Use auto for iterators

This makes the code more readable, and the type is still clear as we are
just calling lower_bound and upper_bound on a multimap.

Author: antlechner

src/util/symbol_table.cpp

@@ -93,10 +93,8 @@ void symbol_tablet::erase(const symbolst::const_iterator &entry)
 {
   const symbolt &symbol=entry->second;
 
-  symbol_base_mapt::const_iterator base_it =
-    symbol_base_map.lower_bound(symbol.base_name);
-  symbol_base_mapt::const_iterator base_it_end =
-    symbol_base_map.upper_bound(symbol.base_name);
+  auto base_it = symbol_base_map.lower_bound(symbol.base_name);
+  auto base_it_end = symbol_base_map.upper_bound(symbol.base_name);
   while(base_it!=base_it_end && base_it->second!=symbol.name)
     ++base_it;
   INVARIANT(
@@ -109,12 +107,8 @@ void symbol_tablet::erase(const symbolst::const_iterator &entry)
 
   if(!symbol.module.empty())
   {
-    symbol_module_mapt::const_iterator module_it =
-                                         symbol_module_map.lower_bound(
-                                           symbol.module),
-                                       module_it_end =
-                                         symbol_module_map.upper_bound(
-                                           symbol.module);
+    auto module_it = symbol_module_map.lower_bound(symbol.module);
+    auto module_it_end = symbol_module_map.upper_bound(symbol.module);
     while(module_it != module_it_end && module_it->second != symbol.name)
       ++module_it;
     INVARIANT(