Make optional logging in http-server

[the-man-with-a-golden-mind]

Just by commenting that one line I can jump with http-server performance from 130-160 requests / second to 612 request / second. https://github.com/ashinn/chibi-scheme/blob/67fdb283b667c8f340a5dc7259eaf44825bc90bc/lib/chibi/net/http-server.scm#L57

[ashinn]

Try (logger-current-level-set! default-logger 'warn).

It probably makes sense to initialize the log level from an environment variable.

[the-man-with-a-golden-mind]

Why logging is so slow? Maybe we can make it async?

[ashinn]

Logging uses custom date formatting written in Scheme and writes all mime headers as an sexp (using the expensive and generalized write).

For now added a --quiet option to disable this. We can also maybe play around with not logging the full headers.