Grave key

[chuckb]

Within the teensy 3 library (and maybe within others...I did not check), the key layout for the grave key is labeled #define KEY_TILDE ( 53 | 0xF000 ). Tilde is emitted with the shift modifier key, so I believe that the name is mis-labeled and should be KEY_GRAVE (or KEY_BACKTICK since some may not recognize the grave reference). I believe that all other key definitions are given with their non-shifted variants.