(EXPERIMENTAL) Fix #624: try to use more efficient String constructor

[cowtowncoder]

[cowtowncoder]

Oddly does not seem to speed up jackson-benchmarks CBOR test (in fact, ~5% slow down).

Maybe new String(byte[], int, int, Charset) not more optimal or... need to do some profiling I suppose.

[cowtowncoder]

Oh. I suspect JDK uses fast method:

byte[] bytes = StringLatin1.encode(chars, 0, chars.length);

to handle conversion.