Use std::thread::hardware_concurrency, instead of Boost, to determine available cores

src/util.cpp

@@ -77,6 +77,7 @@
 #include <openssl/crypto.h>
 #include <openssl/rand.h>
 #include <openssl/conf.h>
+#include <thread>
 
 // Application startup time (used for uptime calculation)
 const int64_t nStartupTime = GetTime();
@@ -891,11 +892,7 @@ bool SetupNetworking()
 
 int GetNumCores()
 {
-#if BOOST_VERSION >= 105600
-    return boost::thread::physical_concurrency();
-#else // Must fall back to hardware_concurrency, which unfortunately counts virtual cores
-    return boost::thread::hardware_concurrency();
-#endif
+    return std::thread::hardware_concurrency();
 }
 
 std::string CopyrightHolders(const std::string& strPrefix)

src/util.h

@@ -295,9 +295,8 @@ std::string HelpMessageGroup(const std::string& message);
 std::string HelpMessageOpt(const std::string& option, const std::string& message);
 
 /**
- * Return the number of physical cores available on the current system.
- * @note This does not count virtual cores, such as those provided by HyperThreading
- * when boost is newer than 1.56.
+ * Return the number of cores available on the current system.
+ * @note This does count virtual cores, such as those provided by HyperThreading.
  */
 int GetNumCores();