Enhance warning output.

Add comment to line GCC points finger at.
This is not intended to fix the warning.
Rather, it is intended to make it clearer
that this may need a deeper review before
determining what (if any) code change would
be appropriate.

Author: henrygab

libraries/USBHost/examples/USB_desc/USB_desc.ino

@@ -209,7 +209,7 @@ byte getconfdescr( byte addr, byte conf )
 {
   uint8_t buf[ BUFSIZE ];
   uint8_t* buf_ptr = buf;
-  byte rcode;
+  byte rcode; // BUGBUG -- code does not actually check return code (no error handling!)
   byte descr_length;
   byte descr_type;
   uint16_t total_length;