Strings

[Mercerenies]

Emacs Calc represents strings as simple vectors of integers. I think I want to represent strings as a concrete (atomic) data type, so we can get proper UTF-8 support.

• [X] String data type (ae1d924)
• [X] String parsing (2805828)
• [X] String output (ae1d924)
• [X] Special input method for literal strings (66ee6d6)
• [X] Built-in operations on strings (like + and *) (ae3ab98)
• [X] Any string-specific helpers (eb29a34)

[Mercerenies]

eb29a34 adds some basic string helpers (upcase and downcase). Closing this issue. We may add more string helpers in the future.