Case functions, case folding and IDNA mappings

[egao1980]

I'm working towards better pure CL support for Unicode. While looking into IDNA libraries I've found that CL-UNICODE is missing few bits that I can fill.

So please review the following changes:

• Unicode data updated to v 13.0.0
• Added the corresponding IDNA mapping data file
• Added canonical character decomposition (single char NFD)
• Fixed case mappings
• Added special case mappings
• Added case folding
• Added IDNA mapping lookup
• Implemented missing Changes_When_* derived properties
• All tests are passing now :)

[stassats]

I'm getting
; Undefined functions:
; CL-UNICODE::CASE-FOLDING-MAPPING CL-UNICODE::DECOMPOSITION-MAPPING

[stassats]

I suppose this is #18

[egao1980]

Yep, it's #18