Introduce UTF matchers into std.uni.

It's a step zero to get decode-less std.regex.

UTF matchers are efficient functors around a set of
specific tries. Processing Unicode characters
without decoding at speeds on par with decoding itself.

Along the way make staticIota at 'package' protected and reuse it.
Fixes a couple of shameful typos.

Some ballpark results with LDC. 
DMD results suck badly, but it never optimized new Tries to begin with so nothing new there.

Tested: 
1. new UTF matchers
2. decode + tried and true internal  trie std.regex 
3. decode + new std.uni trie
4. decode-only
5. count bytes > 0x20

Legend: name [file], count, time (s), throughput (Mb/s)

```
        m8-Alpha [arwiki],    273256 hits,   1.35852, 459.92 Mb/s
      trie-Alpha [arwiki],    273256 hits,   2.35152, 265.70 Mb/s
  new-trie-alpha [arwiki],    273256 hits,   2.27336, 274.84 Mb/s
     decode-only [arwiki],    342832 hits,   1.63872, 381.28 Mb/s
            noop [arwiki],    599328 hits,   0.30504, 2048.28 Mb/s

        m8-Alpha [dewiki],   1435456 hits,   3.84244, 442.65 Mb/s
        trie-Alpha [dewiki],   1435456 hits,   7.92868, 214.52 Mb/s
  new-trie-alpha [dewiki],   1435456 hits,    6.7128, 253.38 Mb/s
     decode-only [dewiki],   1680050 hits,    3.4514, 492.81 Mb/s
            noop [dewiki],   1607454 hits,   0.88392, 1924.23 Mb/s

        m8-Alpha [enwiki],   1152212 hits,   3.90008, 459.83 Mb/s
      trie-Alpha [enwiki],   1152212 hits,   7.90484, 226.87 Mb/s
  new-trie-alpha [enwiki],   1152212 hits,   6.95048, 258.02 Mb/s
     decode-only [enwiki],   1786517 hits,   3.53968, 506.65 Mb/s
            noop [enwiki],   1699856 hits,   0.97012, 1848.61 Mb/s

        m8-Alpha [ruwiki],    414460 hits,    2.0152, 452.02 Mb/s
      trie-Alpha [ruwiki],    414460 hits,   3.34324, 272.46 Mb/s
  new-trie-alpha [ruwiki],    414460 hits,   3.29996, 276.03 Mb/s
     decode-only [ruwiki],    496887 hits,   2.33088, 390.80 Mb/s
            noop [ruwiki],    884374 hits,   0.45652, 1995.31 Mb/s
```