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.
erts: Initialize links when reading file info
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.
erts: Fix SMP for ERTS_OPCODE_COUNTER_SUPPORT

Cleanup macro code.
Fix bug in FreeBSD topology detection code

Code incorrectly relied on undefined C behavior. Clang and gcc 4.9 do not behave
as code expected. This affected cores and processors detection on FreeBSD.
syntax_tools: Refactor away ?line macro
syntax_tools: Strengthen erl_syntax tests

Mostly type and conversion tests.
syntax_tools: Strengthen epp_dodger tests

Mostly epp_dodger smoke tests.
syntax_tools: Fix is_literal/1 for binary
syntax_tools: Teach Maps to erl_syntax

Affected functions:

* erl_syntax:abstract/1
* erl_syntax:concrete/1
* erl_syntax:is_leaf/1
* erl_syntax:is_literal/1
syntax_tools: Strengthen erl_syntax comments tests

Comments in the syntax tree.
Tested via t_epp_dodger.
syntax_tools: Strengthen erl_recomment tests

Also erl_comment_scan tests.
syntax_tools: Strengthen igor tests

Simple test of igor:merge/3
Merge branch 'egil/maps/syntax-tools/OTP-12265' into maint

* egil/maps/syntax-tools/OTP-12265:
  syntax_tools: Strengthen igor tests
  syntax_tools: Strengthen erl_recomment tests
  syntax_tools: Strengthen erl_syntax comments tests
  syntax_tools: Teach Maps to erl_syntax
  syntax_tools: Fix is_literal/1 for binary
  syntax_tools: Strengthen epp_dodger tests
  syntax_tools: Strengthen erl_syntax tests
  syntax_tools: Refactor away ?line macro
Merge branch 'maint'
Merge branch 'egil/fix-instruction-counter'

* egil/fix-instruction-counter:
  erts: Fix SMP for ERTS_OPCODE_COUNTER_SUPPORT
  erts: Add icount build type for opcode counter
erts: Fix return value from erts_maps_get to be const

From "warning: assignment discards qualifiers from pointer target type"