Cosmetic cleanups to SMSDispatcher classes.

Cleaned up some typos and other small fixes in SMSDispatcher in
preparation for checking in my SMS bug fixes. This change doesn't
fix any bugs, but it shouldn't introduce any either.

- Removed unused import statements
- Removed unused private constants and fields
- Fixed typos in Java comments and private constants
- Added generic type parameter to mSTrackers ArrayList
- Removed unnecessary casts
- Fixed indentation of mResultReceiver in SMSDispatcher
- Removed call to get unused smsc in CDMA sendSMS()
- Changed "|=" to "=" in boolean assignment where the variable
  was initialized to false (thus the two operators are equivalent)

Change-Id: Ic19a63a7ef5cdccc7be86043c2a1b863ec8af652