Log Message:
stella: Update to 6.1.2. Unify with libretro-stella.

6.1.1 to 6.1.2: (April 25, 2020)

  * Fixed bug with remapped events not being reloaded in certain cases.

  * Fixed bug in debugger for 3E scheme when displaying active RAM bank.

  * Fixed bug in "Dragon Defender" ROM being misconfigured for Mindlink
    controller.

6.1 to 6.1.1: (April 4, 2020)

  * Fixed crash in 3E bankswitching scheme when writing to ROM addresses.

  * Fix snapshots on Retina HiDPI displays capturing only the top-left
    corner.

  * Fixed wrong color for BK (background) swatch in the debugger.

  * Fixed 'Right Diff' button in Command menu changing left difficulty
    instead.

  * Fixed compilation of libretro port on Debian Buster.