Give threads a recognisable name to aid in debugging

NOTE: These thread names are visible in gdb when using 'info threads'.
      Additionally both 'top' and 'ps' show these names *unless* told to
      display the command-line instead of task name.

Signed-off-by: Giel van Schijndel <me@mortis.eu>

src/main.cpp

@@ -3594,6 +3594,9 @@ void static BitcoinMiner(CWallet *pwallet)
     printf("BitcoinMiner started\n");
     SetThreadPriority(THREAD_PRIORITY_LOWEST);
 
+    // Make this thread recognisable as the mining thread
+    RenameThread("bitcoin [miner]");
+
     // Each thread has its own key and counter
     CReserveKey reservekey(pwallet);
     unsigned int nExtraNonce = 0;