Improve `D` (decimal) atom

[Reconcyl]

Make D (to decimal) take the ord first if given a character.

[GolfingSuccess]

@ScratchMan544 Why should it take the ordinal of a character and not just the digit the character itself represents ([0-9]) or 0 if the character is not a digit? That's how bit-wise functions (&, |, ^, ~) behave.

[Reconcyl]

Taking the digit the character represents is not a particularly useful operation in this cae – after all, we're converting to decimal, so that would essentially just be an "eval". The reason I chose the ordinal is because that's what I actually found useful when golfing.