Put the details consistently with event datatypes, instead
of trying to put them all in `sync', which better reflects
the extensibility of the set of synchronizable events.
A phantom byte string is a small object that the memory
manager treats as an arbitrary-sized object, where the
size is specified when the phantom byte string is created
or or when size is changed via `set-phantom-bytes!'.
The `make-log-receiver' function now includes a logger-name
filter. This filter is implemented as a low enough level that
it affects `log-level?' tests to check whether a log message
needs to be constructed at all.
The -W and -L flags and PLTSTDERR and PLTSYSLOG environment variables
support filters of the form "<level> <level>@<name> ...", where
<level>@<name> specializes filtering of events for a logger whose
name matches <name> to show <level> and higher.
Show process time of start of GC and otherwise adjust to make
the output more compact, and attach a prefab struct to the
logged message to report all available data in Racket form
(including real start and end times, which are not shown in
the output).
