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/walletdb.cpp

@@ -323,6 +323,9 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
 
 void ThreadFlushWalletDB(void* parg)
 {
+    // Make this thread recognisable as the wallet flushing thread
+    RenameThread("bitcoin-wallet");
+
     const string& strFile = ((const string*)parg)[0];
     static bool fOneThread;
     if (fOneThread)