message: lpng is required for windows
diff: @@ -56,6 +56,7 @@ contains(USE_QRCODE, 1) {
  message(Building with QRCode support)
  DEFINES += USE_QRCODE
  LIBS += -lqrencode
  + win32:LIBS += -lpng
  }
  # use: qmake "USE_UPNP=1" ( enabled by default; default)
  