rtlil, hashlib: Remove deprecated std::iterator usage

`std::iterator` has been deprecated in C++17. Yosys is being compiled
against the C++11 standard but plugins can opt to compile against a
newer one. To silence some deprecation warnings when those plugins are
being compiled, replace the `std::iterator` inheritance with the
equivalent type declarations.

kernel/hashlib.h

@@ -371,14 +371,18 @@ class dict
 	}
 
 public:
-	class const_iterator : public std::iterator<std::forward_iterator_tag, std::pair<K, T>>
+	class const_iterator
 	{
 		friend class dict;
 	protected:
 		const dict *ptr;
 		int index;
 		const_iterator(const dict *ptr, int index) : ptr(ptr), index(index) { }
 	public:
+		typedef std::pair<K, T> value_type;
+		typedef ptrdiff_t difference_type;
+		typedef std::pair<K, T>* pointer;
+		typedef std::pair<K, T>& reference;
 		const_iterator() { }
 		const_iterator operator++() { index--; return *this; }
 		const_iterator operator+=(int amt) { index -= amt; return *this; }
@@ -389,14 +393,19 @@ class dict
 		const std::pair<K, T> *operator->() const { return &ptr->entries[index].udata; }
 	};
 
-	class iterator : public std::iterator<std::forward_iterator_tag, std::pair<K, T>>
+	class iterator
 	{
 		friend class dict;
 	protected:
 		dict *ptr;
 		int index;
 		iterator(dict *ptr, int index) : ptr(ptr), index(index) { }
 	public:
+		typedef std::forward_iterator_tag iterator_category;
+		typedef std::pair<K, T> value_type;
+		typedef ptrdiff_t difference_type;
+		typedef std::pair<K, T>* pointer;
+		typedef std::pair<K, T>& reference;
 		iterator() { }
 		iterator operator++() { index--; return *this; }
 		iterator operator+=(int amt) { index -= amt; return *this; }
@@ -800,14 +809,19 @@ class pool
 	}
 
 public:
-	class const_iterator : public std::iterator<std::forward_iterator_tag, K>
+	class const_iterator
 	{
 		friend class pool;
 	protected:
 		const pool *ptr;
 		int index;
 		const_iterator(const pool *ptr, int index) : ptr(ptr), index(index) { }
 	public:
+		typedef std::forward_iterator_tag iterator_category;
+		typedef K value_type;
+		typedef ptrdiff_t difference_type;
+		typedef K* pointer;
+		typedef K& reference;
 		const_iterator() { }
 		const_iterator operator++() { index--; return *this; }
 		bool operator==(const const_iterator &other) const { return index == other.index; }
@@ -816,14 +830,19 @@ class pool
 		const K *operator->() const { return &ptr->entries[index].udata; }
 	};
 
-	class iterator : public std::iterator<std::forward_iterator_tag, K>
+	class iterator
 	{
 		friend class pool;
 	protected:
 		pool *ptr;
 		int index;
 		iterator(pool *ptr, int index) : ptr(ptr), index(index) { }
 	public:
+		typedef std::forward_iterator_tag iterator_category;
+		typedef K value_type;
+		typedef ptrdiff_t difference_type;
+		typedef K* pointer;
+		typedef K& reference;
 		iterator() { }
 		iterator operator++() { index--; return *this; }
 		bool operator==(const iterator &other) const { return index == other.index; }
@@ -1021,14 +1040,18 @@ class idict
 	pool<K, OPS> database;
 
 public:
-	class const_iterator : public std::iterator<std::forward_iterator_tag, K>
+	class const_iterator
 	{
 		friend class idict;
 	protected:
 		const idict &container;
 		int index;
 		const_iterator(const idict &container, int index) : container(container), index(index) { }
 	public:
+		typedef K value_type;
+		typedef ptrdiff_t difference_type;
+		typedef K* pointer;
+		typedef K& reference;
 		const_iterator() { }
 		const_iterator operator++() { index++; return *this; }
 		bool operator==(const const_iterator &other) const { return index == other.index; }

kernel/rtlil.h

@@ -803,8 +803,14 @@ struct RTLIL::SigBit
 	unsigned int hash() const;
 };
 
-struct RTLIL::SigSpecIterator : public std::iterator<std::input_iterator_tag, RTLIL::SigSpec>
+struct RTLIL::SigSpecIterator
 {
+	typedef std::input_iterator_tag iterator_category;
+	typedef RTLIL::SigSpec value_type;
+	typedef ptrdiff_t difference_type;
+	typedef RTLIL::SigSpec* pointer;
+	typedef RTLIL::SigSpec& reference;
+
 	RTLIL::SigSpec *sig_p;
 	int index;
 
@@ -814,8 +820,14 @@ struct RTLIL::SigSpecIterator : public std::iterator<std::input_iterator_tag, RT
 	inline void operator++() { index++; }
 };
 
-struct RTLIL::SigSpecConstIterator : public std::iterator<std::input_iterator_tag, RTLIL::SigSpec>
+struct RTLIL::SigSpecConstIterator
 {
+	typedef std::input_iterator_tag iterator_category;
+	typedef RTLIL::SigSpec value_type;
+	typedef ptrdiff_t difference_type;
+	typedef RTLIL::SigSpec* pointer;
+	typedef RTLIL::SigSpec& reference;
+
 	const RTLIL::SigSpec *sig_p;
 	int index;