stap: dump the command along with the script with `-D`
log: don't display time
io: display top accessed files
Change `encoding` to `config` in file headers.
php: add backtrace profiling
stap: allow to specify several STAP options

Because such options can start with `-`, it is difficult to use
`nargs='+'`. Therefore, we allow the option to be specified several
times instead.
stap: allow to specify modules from which to load unwind data
php: build backtrace by examining `executor_globals` at current point
php: also display C backtrace when requested