wallet: Use boost to more portably ensure -wallet specifies only a filename

src/wallet/wallet.cpp

@@ -3765,7 +3765,7 @@ bool CWallet::InitLoadWallet()
 
     std::string walletFile = GetArg("-wallet", DEFAULT_WALLET_DAT);
 
-    if (walletFile.find_first_of("/\\") != std::string::npos) {
+    if (boost::filesystem::path(walletFile).filename() != walletFile) {
         return InitError(_("-wallet parameter must only specify a filename (not a path)"));
     } else if (SanitizeString(walletFile, SAFE_CHARS_FILENAME) != walletFile) {
         return InitError(_("Invalid characters in -wallet filename"));