* Fixes allowing for “Full” folding and NFKC_CaseFold compliance.
* Only include C (Common) and F (Full) foldings from CaseFolding.txt. Removed S (Simple) since F & S are specified to be exclusive.
* Extend UTF8PROC_IGNORE to also ignore unassigned codepoints (such as \u2065) which are specified as being discarded by NFKC_CF.
* Document the changes to UTF8PROC_IGNORE in header.
* Add NFKC_CF helper function with documentation.
* restore old IGNORE behavior, add UTF8PROC_STRIPNA, rename to utf8proc_NFKC_Casefold, add a test
* success message
* test that IGNORE does not strip NA
* data update
* NFKC_Casefold shouldn't strip NA
* new utf8proc_map_custom for hooking in user-defined custom mappings
* whoops, add test program
* NEWS, version bump for 2.1
* change test functions to static so that gcc doesn't complain about missing prototypes
