Running this test when for some reason stdlib has been
unstickied could cause the emulator to die. So we check first
to make sure that the expected files are sticky.

Performance for processes that receive huge amounts of
messages can be increased by storing the incoming messages
outside the heap (that avoids copying the message in a
garbage collection).

Two OTP processes that are known to receive many messages
are 'rex' (used by 'rpc') and 'error_logger'.

Extend file_SUITE:read_write_file/1 to test file:write_file/3
which was not tested at all.

While we are it, remove the superfluous roundtrips tests of
term_to_binary/1 and binary_to_term/1. Those BIFs are tested
in detail in other test suites (for example, binary_SUITE in
emulator_test).

* raimo/diffserv-socket-option/OTP-13582:
  Tune 'tclass' semantics
  Implement IPV6_TCLASS

Normally, calling code:delete/1 before re-loading the code for a
module is unnecessary but causes no problem.

But there will be be problems if the new code has an on_load function.
Code with an on_load function will always be loaded as old code
to allowed it to be easily purged if the on_load function would fail.
If the on_load function succeeds, the old and current code will be
swapped.

So in the scenario where code:delete/1 has been called explicitly,
there is old code but no current code. Loading code with an
on_load function will cause the reference to the old code to be
overwritten. That will at best cause a memory leak, and at worst
an emulator crash (especially if NIFs are involved).

To avoid that situation, we will put the code with the on_load
function in a special, third slot in Module.

ERL-240

* lukas/kernel/os_cmd_fix_stdin_close/OTP-13867:
  kernel: Close stdin of commands run in os:cmd

This is needed when running programs that only exit when
stdin has been closed, e.g. 'more'.