ICU-free ada

[lemire]

Replaces ICU by our own implementation.

Fixes #89

[anonrig]

Really good! Let's wait for merging since we might need to release a new version before pushing ada/idna to production.

[lemire]

Ada/idna is faster than ICU by about 10%. And many further optimizations are possible.

ada/idna

$ ./buildidna/benchmarks/wpt_bench tests/wpt/urltestdata.json 
BasicBench_AdaURL     418546 ns       418578 ns         1667 GHz=3.3941 cycle/byte=60.3839 cycles/url=1.8774k instructions/byte=106.133 instructions/cycle=1.75763 instructions/ns=5.96559 instructions/url=3.29979k ns/url=553.137 speed=56.2284M/s time/byte=17.7846ns time/url=552.944ns url/s=1.8085M/s

ICU

$ ./buildmain/benchmarks/wpt_bench 
----------------------------------------------------------------------------
Benchmark                  Time             CPU   Iterations UserCounters...
----------------------------------------------------------------------------
BasicBench_AdaURL     480858 ns       480899 ns         1466 GHz=3.39432 cycle/byte=66.5358 cycles/url=2.06867k instructions/byte=114.044 instructions/cycle=1.71402 instructions/ns=5.81792 instructions/url=3.54574k ns/url=609.452 speed=48.9417M/s time/byte=20.4325ns time/url=635.269ns url/s=1.57414M/s