Rename Delphi to Pascal

Certain repositories (like https://github.com/graemeg/freepascal) are being shown as being written in Delphi instead of Pascal.

While Delphi is technically a different language to Pascal, I think it's still appropriate to call Delphi code Pascal, even if it may not be appropriate to call non-Delphi Pascal code (like a self-hosting Pascal compiler) Delphi. (does that make sense?)

cc @tnm