Fixes the symbol_base_tablet iterator

The iterator for symbol_base_tablet had a missing operator overload
which prevented range-based loops from working

Commit also adds a unit-test

Author: Degiorgio

src/util/symbol_table_base.h

@@ -144,6 +144,11 @@ class symbol_table_baset
     typedef symbolst::const_iterator::reference reference;           // NOLINT
     typedef symbolst::iterator::iterator_category iterator_category; // NOLINT
 
+    bool operator!=(const iteratort &other) const
+    {
+      return it != other.it;
+    }
+
     bool operator==(const iteratort &other) const
     {
       return it == other.it;

unit/util/symbol_table.cpp

@@ -5,6 +5,25 @@
 #include <testing-utils/catch.hpp>
 #include <util/journalling_symbol_table.h>
 
+TEST_CASE("Iterating through a symbol table", "[core][utils][symbol_tablet]")
+{
+  symbol_tablet symbol_table;
+
+  symbolt symbol;
+  irep_idt symbol_name = "Test";
+  symbol.name = symbol_name;
+
+  symbol_table.insert(symbol);
+
+  int counter = 0;
+  for(auto &entry : symbol_table)
+  {
+    ++counter;
+  }
+
+  REQUIRE(counter == 1);
+}
+
 SCENARIO("journalling_symbol_table_writer",
   "[core][utils][journalling_symbol_table_writer]")
 {