scripts/kernelng: example: only close the outfile if needed

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
kngclick: make verbose-level setting eager

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
add and utilize auto-tracing APIs

This adds the decorators auto_trace_function and auto_trace_method,
which automatically output call tracing data to stderr for the decorated
function or method, respectively, when the verbose level is --debug.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
output: lazy trace formatting

As implemented, the trace decorators add a ton of useless overhead when
not in --debug mode, because they calculate all the formatting, and then
discard it when the trace level is too low.  Change the _at.say API to
expect a zero-argument lambda expression instead of a string, and only
invoke it when needed, to (hopefully) mostly fix this.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>