Adding dynamic USB power support

- Each scan module now has a current change callback which passes the available current as a parameter
- No longer attempts to use the max 500 mA immediately, starts with 100 mA then goes to 500 mA after enumeration
- If enumeration fails due to bMaxPower of 500 mA, then attempt again at 100 mA (might also be possible to go even lower to 20 mA in certain cases)
- Now working with the Apple Ipad (no over-power messages)
- Fixed Wake-up behaviour on Apple Ipad (and likely other iOS devices)
- More effecient set_feature/clear_feature handling (device handler)
- Initial power handling via Interconnect (still needs work to get it more dynamic)

Scan/MDErgo1/scan_loop.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2014-2015 by Jacob Alexander
+/* Copyright (C) 2014-2016 by Jacob Alexander
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -31,10 +31,12 @@
 // ----- Functions -----
 
 // Functions to be called by main.c
-void Scan_setup( void );
-uint8_t Scan_loop( void );
+void Scan_setup();
+uint8_t Scan_loop();
 
 // Call-backs
 void Scan_finishedWithMacro( uint8_t sentKeys );  // Called by Macro Module
 void Scan_finishedWithOutput( uint8_t sentKeys ); // Called by Output Module
 
+void Scan_currentChange( unsigned int current ); // Called by Output Module
+