Fix spelling typos in comments. (#530)

include/platform/misc.h

@@ -29,7 +29,7 @@
 /**
  * @file
  * @brief
- *   This file includes platform abstractions for miscelaneous behaviors.
+ *   This file includes platform abstractions for miscellaneous behaviors.
  */
 
 #ifndef OT_PLATFORM_MISC_H

include/platform/radio.h

@@ -120,7 +120,7 @@ typedef enum PhyState
  * The following are valid radio state transitions:
  *
  *                                    (Radio ON)
- *  +----------+  Enable()  +-------+  Receive() +---------+   Trasnmit()  +----------+
+ *  +----------+  Enable()  +-------+  Receive() +---------+   Transmit()  +----------+
  *  |          |----------->|       |----------->|         |-------------->|          |
  *  | Disabled |            | Sleep |            | Receive |               | Transmit |
  *  |          |<-----------|       |<-----------|         |<--------------|          |
@@ -240,7 +240,7 @@ ThreadError otPlatRadioReceive(uint8_t aChannel);
 extern void otPlatRadioReceiveDone(RadioPacket *aPacket, ThreadError aError);
 
 /**
- * The radio tranitions from Transmit to Receive.
+ * The radio transitions from Transmit to Receive.
  * This method returns a pointer to the transmit buffer.
  *
  * The caller forms the IEEE 802.15.4 frame in this buffer then calls otPlatRadioTransmit() to request transmission.

include/platform/settings.h

@@ -113,7 +113,7 @@ ThreadError otPlatSettingsAbandonChange(void);
  *  aValueLength. The initial value of aValueLength is the
  *  maximum number of bytes to be written to aValue.
  *
- *  This function can be used to check for the existance of
+ *  This function can be used to check for the existence of
  *  a key without fetching the value by setting aValue and
  *  aValueLength to NULL. You can also check the length of
  *  the setting without fetching it by setting only aValue
@@ -214,7 +214,7 @@ ThreadError otPlatSettingsAdd(uint16_t aKey, const uint8_t *aValue, int aValueLe
  *  that is required to maintain the relative order of the
  *  values associated with aKey. For example, if you have three
  *  items ordered (A, B, C) and you delete B, the resulting order
- *  is guarateed to be (A, C).
+ *  is guaranteed to be (A, C).
  *
  *  @param[in] aKey
  *             The key associated with the requested setting.