RetroArch: Flip phone overlay

[XerTheSquirrel]

Cross referencing: libretro/common-overlays#39

A new overlay for flip phone device emulation is needed (currently by SquirrelJME). Note that any overlays for ColecoVision, Intellivision, and Atari Jaguar systems will not work here due to lack of information on buttons and the number of available buttons.

Specifically the following keys are required:

• Up
• Down
• Left
• Right
• Select
• Soft 1 (Top-left button)
• Soft 2 (Top-right button)
• Talk/Call (vertical green phone facing left)
• End/Hangup (horizontal red phone facing down)
• Camera
• Back
• Speaker
• Volume Up
• Volume Down
• 1 🖂 or 1 ➿ (Voicemail)
• 2 ABC
• 3 DEF
• 4 GHI
• 5 JKL (tactile aid)
• 6 MNO
• 7 PQRS
• 8 TUV
• 9 WXYZ
• * Shift (Star, Shift)
• One of these pairs:
  • Space on zero:
    • 0 + ␣ (Zero, Plus, Space)
    • # (Pound)
  • Space on pound:
    • 0 + (Zero, Plus)
    • # ␣ (Pound, Space)

This can be seen in the following picture of a Kyocera Dura XT:

[XerTheSquirrel]

Closed by libretro/common-overlays@ecccb45.