Merge pull request arduino#76 from dmadison/pluggable-unused

Fix unused variable warning for non-pluggable USB in SendDescriptor

Author: aentinger

cores/arduino/USBCore.cpp

@@ -496,14 +496,13 @@ bool SendConfiguration(int maxlen)
 static
 bool SendDescriptor(USBSetup& setup)
 {
-int ret;
 u8 t = setup.wValueH;
 if (USB_CONFIGURATION_DESCRIPTOR_TYPE == t)
 return SendConfiguration(setup.wLength);
 
 InitControl(setup.wLength);
 #ifdef PLUGGABLE_USB_ENABLED
-ret = PluggableUSB().getDescriptor(setup);
+int ret = PluggableUSB().getDescriptor(setup);
 if (ret != 0) {
 return (ret > 0 ? true : false);
 }