Performance update to appendJSONString so that it now checks if
the input is a simple string that contains no json delimiters, control
characters, or unicode. If simple then the operation is only three
appends. [double-quote, string, double-quote].
If a non-simple character is encountered then all of the previous
characters are appended and the operation falls back to the original
method for the remaining characters.
Before:
BenchmarkLogEmpty-8 100000000 17.1 ns/op
BenchmarkDisabled-8 500000000 4.12 ns/op
BenchmarkInfo-8 20000000 101 ns/op
BenchmarkContextFields-8 20000000 105 ns/op
BenchmarkLogFields-8 5000000 281 ns/op
After:
BenchmarkLogEmpty-8 100000000 16.7 ns/op
BenchmarkDisabled-8 500000000 3.79 ns/op
BenchmarkInfo-8 30000000 44.8 ns/op
BenchmarkContextFields-8 30000000 67.5 ns/op
BenchmarkLogFields-8 10000000 197 ns/op