Support API 23 methods in MBC and MBSC

- Use an extra messenger between MBSC (MediaBrowserServiceCompat)
  and MBC (MediaBrowserCompat) when the platform SDK version is
  21 or 22 in order to support the new method added in API 23.
- Use version numbers for better forward compatibility.

Bug: 22917960
Change-Id: Idf4247ee78ebfcf34434b92531618cc35151d038
8 files changed