Jumping around in a compressed file is nowhere near as cheap as
for uncompressed files, as it requires reading and decompressing
up until the desired position. Using read_ahead will improve
performance slightly.

into sverker/maint/ets-no-mbuf-trapping/OTP-15660

Many heap fragments do no longer make the GC slow.

Even worse, we are not guaranteed that a yield will provoke a GC
removing the fragments, which might lead to a one-yield-per-bucket
scenario if the heap fragment(s) still remains after each yield.

Avoid traversing all of the list/string when only part of it will be
used. An explicit check that the list is flat is needed since
string:slice() accepts deep lists and more.

* hasse/stdlib/optimize_calendar_rfc3339/OTP-15630:
  stdlib: Optimize calendar:system_time_to_rfc3339()

The phrasing "no process can access the ETS table in the middle of the
operation" implies that the entire table is looked during
the operation, which is not true if `write_concurrency`
is enabled.

Not using io_lib for formatting makes the conversion several times
faster.

Long atom names in combination with <c><<>></c> could cause a crash.