Fix CUtlHashMap initialization bug.

Fix a pretty sharp edge: when inserting into CUtlHashMap with a function that
only takes a key and inserts the default value, we were using "default
initialization" ("new T"), which does not initialize PODs.  Switch to
"value initialization" ("new T{}").

Also some minor compiler compatibility fixes.  The version of gcc we're using
here didn't like the {}-style call of the base class constructor, so use ()
instead.  *shrug*

Also deleted a kludge for an older version of Visual Studio.  We were
supporting that for a while in Steam, but we've upgraded our min specs and
so I'm doing the same here.

src/public/tier0/platform.h

@@ -155,6 +155,8 @@ PLATFORM_INTERFACE bool Plat_IsInDebugSession();
 // Methods to invoke the constructor, copy constructor, and destructor
 //-----------------------------------------------------------------------------
 
+// Placement new, using "default initialization".
+// THIS DOES NOT INITIALIZE PODS!
 template <class T> 
 inline void Construct( T* pMemory )
 {
@@ -162,6 +164,15 @@ inline void Construct( T* pMemory )
 	::new( pMemory ) T;
 }
 
+// Placement new, using "value initialization".
+// This will zero-initialize PODs
+template <class T>
+inline T* ValueInitializeConstruct( T* pMemory )
+{
+	HINT( pMemory != 0 );
+	return ::new( pMemory ) T{};
+}
+
 template <class T> 
 inline void CopyConstruct( T* pMemory, T const& src )
 {

src/public/tier1/utlhashmap.h

@@ -267,7 +267,7 @@ public:
 		Node_t &m_node;
 		const int m_idx;
 	public:
-		inline ItemRef( const CUtlHashMap< K, T, L, H > &map, int idx ) : m_node{ const_cast< Node_t &>( map.m_memNodes[idx] ) }, m_idx{idx} {}
+		inline ItemRef( const CUtlHashMap< K, T, L, H > &map, int idx ) : m_node( const_cast< Node_t &>( map.m_memNodes[idx] ) ), m_idx(idx) {}
 		ItemRef( const ItemRef &x ) = default;
 		inline int Index() const { return m_idx; }
 		inline const KeyType_t &Key() { return m_node.m_key; }
@@ -275,7 +275,7 @@ public:
 	};
 	struct MutableItemRef : ItemRef
 	{
-		inline MutableItemRef( CUtlHashMap< K, T, L, H > &map, int idx ) : ItemRef{ map, idx } {}
+		inline MutableItemRef( CUtlHashMap< K, T, L, H > &map, int idx ) : ItemRef( map, idx ) {}
 		MutableItemRef( const MutableItemRef &x ) = default;
 		using ItemRef::Element; // const reference
 		inline ElemType_t &Element() const { return this->m_node.m_elem; } // non-const reference
@@ -288,7 +288,7 @@ public:
 		CUtlHashMap<K, T, L, H > &m_map;
 		int m_idx;
 	public:
-		inline Iterator( const CUtlHashMap< K, T, L, H > &map, int idx ) : m_map{ const_cast< CUtlHashMap< K, T, L, H > &>( map ) }, m_idx{idx} {}
+		inline Iterator( const CUtlHashMap< K, T, L, H > &map, int idx ) : m_map( const_cast< CUtlHashMap< K, T, L, H > &>( map ) ), m_idx(idx) {}
 		Iterator( const Iterator &x ) = default;
 		inline bool operator==( const Iterator &x ) const { return &m_map == &x.m_map && m_idx == x.m_idx; } // Comparing the map reference is probably not necessary in 99% of cases, but needed to be correct
 		inline bool operator!=( const Iterator &x ) const { return &m_map != &x.m_map || m_idx != x.m_idx; }
@@ -463,7 +463,7 @@ inline int CUtlHashMap<K,T,L,H>::FindOrInsert( const KeyType_t &key )
 	int iNodeInserted = InsertUnconstructed( key, &iNodeExisting, false /*no duplicates allowed*/ ); // copies key
 	if ( iNodeInserted != kInvalidIndex )
 	{
-		Construct( &m_memNodes[ iNodeInserted ].m_elem );
+		ValueInitializeConstruct( &m_memNodes[ iNodeInserted ].m_elem );
 		return iNodeInserted;
 	}
 	return iNodeExisting;
@@ -497,7 +497,7 @@ inline int CUtlHashMap<K,T,L,H>::InsertOrReplace( const KeyType_t &key )
 	int iNodeInserted = InsertUnconstructed( key, &iNodeExisting, false /*no duplicates allowed*/ ); // copies key
 	if ( iNodeInserted != kInvalidIndex )
 	{
-		Construct( &m_memNodes[ iNodeInserted ].m_elem );
+		ValueInitializeConstruct( &m_memNodes[ iNodeInserted ].m_elem );
 		return iNodeInserted;
 	}
 	return iNodeExisting;

src/steamnetworkingsockets/clientlib/steamnetworkingsockets_snp.cpp

@@ -9,13 +9,6 @@
 #include <steam/isteamnetworking.h>
 #endif
 
-// Ug
-#ifdef _MSC_VER
-	#if _MSC_VER < 1900
-		#define constexpr const
-	#endif
-#endif
-
 // Acks may be delayed.  This controls the precision used on the wire to encode the delay time.
 constexpr int k_nAckDelayPrecisionShift = 5;
 constexpr SteamNetworkingMicroseconds k_usecAckDelayPrecision = (1 << k_nAckDelayPrecisionShift );