* 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
* convert sequences to utf-16 (saves 25kb)
* store sequence length in properties instead using -1 termination (saves 10kb)
* cache index for slightly faster data creation
* store lower/upper/title mapping in sequence array (saves 25kb). Add utf8proc_totitle, as title_mapping cannot be used to get the title codepoint anymore. Rename xxx_mapping to xxx_seqindex, so programs assuming a value with the old meaning fail at compile time
* change combination array data type to uint16 (saves 40kb)
* merge 1st and 2nd comb index (saves 50kb)
* kill empty prefix/suffix in combination array (saves 50kb)
* there was no need to have a separate combination start array, it can be merged in a single array
* some fixes
* mark the table as const again
* and regen
