Return pointer to value in erts_maps_get()

While at it, implement erts_maps_get_rel() for halfword support.
Support maps in ms_transform
Properly support maps in match_specs
erts: Add icount build type for opcode counter

Enables ERTS_OPCODE_COUNTER_SUPPORT.
Passing global var to QuickCheck statemachine

The data_dir used by the tests is given at runtime. This has as a
disadvantage that the generate test has a hardcoded data_dir in it
(ssh_eqc_client_server_dirs below):

[{set,{var,1},
{call,ssh_eqc_client_server,initial_state,
[{state,false,[],[],[],[],"ssh_eqc_client_server_dirs"}]}},
{set,{var,2},
{call,ssh_eqc_client_server,ssh_server,
[{{127,1,1,1},
{call,ssh_eqc_client_server,inet_port,[{127,1,1,1}]}},
"ssh_eqc_client_server_dirs",
[{parallel_login,true}]]}},

Re-running this tests on another machine works, since the path is
relative, but if it were absolute, it would have been hard.

Instead, we may use a symbolic representation of the data_dir and fill
it in each time one runs the property, thus even when one does a check
or recheck.

The key to this is to use a variable in the test and bind the variable
in the place where one runs the commands by using the environment
variable feature of run_commands.

Conflicts:

	lib/ssh/test/property_test/ssh_eqc_client_server.erl
No side effects in function arguments

We want to be able to see tests with eqc_gen:sample, we also want to be
able to re-run tests.

Side effects are no good idea if these goals need to be met. Therefore,
we replace the side effect to ask for a port by making a symbolic call
of this.

Nicer solutions are possible, but at least we can now re-run the test
case, and therefore shrink.
Reduce the total testing time for the properties to 20 seconds

We need to make a global budget for testing on CI server and then
define for each property how much it may use of that time. Probably in
auxiliary file, such that it can be computed from what has changed in
the repo.
Add timeout to a property test (Thanks John & Tobias @ QuviQ)
ssh_eqc_encode_decode.erl compiles
Optimizations
erts: Initialize links when reading file info
Introduce support for eager check I/O scheduling
Merge branch 'rickard/eager-check-io/OTP-12117' into rickard/maint-17/eager-check-io/OTP-12117

* rickard/eager-check-io/OTP-12117:
  Introduce support for eager check I/O scheduling

Conflicts:
	erts/emulator/beam/erl_bif_info.c
	erts/emulator/beam/erl_init.c
	erts/emulator/beam/erl_process.c
	erts/preloaded/ebin/erlang.beam
No eager check I/O on OSE
Merge branch 'rickard/maint-17/eager-check-io/OTP-12117' into rickard/master/eager-check-io/OTP-12117

* rickard/maint-17/eager-check-io/OTP-12117:
  No eager check I/O on OSE
  Introduce support for eager check I/O scheduling

Conflicts:
	erts/preloaded/ebin/erlang.beam
Change default to "eager check I/O"

Conflicts:
	erts/emulator/beam/erl_process.c
Fix missing field initializer in ERL_NIF_INIT macro

In the ERL_NIF_INIT macro, add a missing static initializer for the new
options field which was added to the ErlNifEntry struct for 17.3. This fix
prevents compile-time errors in NIFs when the compiler is instructed to
treat missing field initializers as errors.
Specify tar-file as basename in upgrade_SUITE

Earlier, the tar-file containing the to-release was specified with
absolut path. The correct way to do this is instead to copy the file
to the $ROOT/releases directory and only specify the basename of the
file in the call to release_handler:unpack_release/1.
compiler: Type map optimization
compiler: Type is_nonempty_list optimization