[avr] Small comments and headers fixes in SPI

Author: cmaglie

libraries/SPI/SPI.cpp

@@ -1,6 +1,7 @@
 /*
  * Copyright (c) 2010 by Cristian Maglie <c.maglie@bug.st>
  * Copyright (c) 2014 by Paul Stoffregen <paul@pjrc.com> (Transaction API)
+ * Copyright (c) 2014 by Matthijs Kooijman <matthijs@stdin.nl> (SPISettings AVR)
  * SPI Master library for arduino.
  *
  * This file is free software; you can redistribute it and/or modify

libraries/SPI/SPI.h

@@ -21,7 +21,7 @@
 
 // Uncomment this line to add detection of mismatched begin/end transactions.
 // A mismatch occurs if other libraries fail to use SPI.endTransaction() for
-// each SPI.beginTransaction().  Connect a LED to this pin.  The LED will turn
+// each SPI.beginTransaction().  Connect an LED to this pin.  The LED will turn
 // on if any mismatch is ever detected.
 //#define SPI_TRANSACTION_MISMATCH_LED 5
 
@@ -147,7 +147,7 @@ class SPIClass {
   // Initialize the SPI library
   static void begin();
 
-  // If SPI is to used from within an interrupt, this function registers
+  // If SPI is used from within an interrupt, this function registers
   // that interrupt with the SPI library, so beginTransaction() can
   // prevent conflicts.  The input interruptNumber is the number used
   // with attachInterrupt.  If SPI is used from a different interrupt