TTY: frameworks/base changes

This CL makes the following changes:
  1. New public APIs:
    - TelecommManager.getCurrentTtyMode: This is used to
      get current TTY mode. It's used by Telephony to set
      the phone state before calls are created (which is why
      it can't be a Conneciton API).
    - TelecommConstants.TTY_MODE_*: These are constants
      copied from Phone.java
    - TelecommConstants.ACTION_CURRENT_TTY_MODE_CHANGED: This
      action is fired when the current TTY mode changes.
      Apps can listen to this before and during a call.
      The old version of this was in TtyIntent.java which
      I deleted.

  2. New private API
    - TelecommManager.isTtySupported: This is used by
      Telephony to hide the TTY settings on devices
      that don't support TTY

  3. Various updates to use the constants renamed in this CL

Change-Id: I652b095af30cc2732a06829dc23492e5355660da
8 files changed