Communication between Erlang processes has conceptually always been
performed through asynchronous signaling. The runtime system
implementation has however previously preformed most operation
synchronously. In a system with only one true thread of execution, this
is not problematic (often the opposite). In a system with multiple threads
of execution (as current runtime system implementation with SMP support)
it becomes problematic. This since it often involves locking of structures
when updating them which in turn cause resource contention. Utilizing
true asynchronous communication often avoids these resource contention
issues.

The case that triggered this change was contention on the link lock due
to frequent updates of the monitor trees during communication with a
frequently used server. The signal order delivery guarantees of the
language makes it hard to change the implementation of only some signals
to use true asynchronous signaling. Therefore the implementations
of (almost) all signals have been changed.

Currently the following signals have been implemented as true
asynchronous signals:
- Message signals
- Exit signals
- Monitor signals
- Demonitor signals
- Monitor triggered signals (DOWN, CHANGE, etc)
- Link signals
- Unlink signals
- Group leader signals

All of the above already defined as asynchronous signals in the
language. The implementation of messages signals was quite
asynchronous to begin with, but had quite strict delivery constraints
due to the ordering guarantees of signals between a pair of processes.

The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts
that service all kinds of signals. More details regarding the signal
queue can be found in comments in the erl_proc_sig_queue.h file.

The monitor and link implementations have also been completely replaced
in order to fit the new asynchronous signaling implementation as good
as possible. More details regarding the new monitor and link
implementations can be found in the erl_monitor_link.h file.

binary:bin_to_list had a poor implementation that resulted in
excessive garbage collection. binary_to_list is almost identical and
has a generally better implementation, so I've replaced
binary:bin_to_list's CIF with a thin wrapper around binary_to_list.

Granted, binary_to_list has a deprecated indexing scheme, but we're
unlikely to ever remote it entirely and it's somewhat easy to move
it to the 'binary' module later on.

* maint:
  Update primary bootstrap

Conflicts:
	bootstrap/bin/start.boot
	bootstrap/bin/start_clean.boot
	bootstrap/lib/compiler/ebin/beam_asm.beam
	bootstrap/lib/compiler/ebin/beam_jump.beam
	bootstrap/lib/compiler/ebin/beam_listing.beam
	bootstrap/lib/compiler/ebin/beam_type.beam
	bootstrap/lib/compiler/ebin/beam_validator.beam
	bootstrap/lib/compiler/ebin/compile.beam
	bootstrap/lib/compiler/ebin/core_pp.beam
	bootstrap/lib/compiler/ebin/v3_codegen.beam
	bootstrap/lib/compiler/ebin/v3_kernel_pp.beam
	bootstrap/lib/kernel/ebin/dist_util.beam
	bootstrap/lib/kernel/ebin/error_logger.beam
	bootstrap/lib/kernel/ebin/erts_debug.beam
	bootstrap/lib/kernel/ebin/group_history.beam
	bootstrap/lib/kernel/ebin/hipe_unified_loader.beam
	bootstrap/lib/kernel/ebin/kernel.app
	bootstrap/lib/kernel/ebin/os.beam
	bootstrap/lib/kernel/ebin/user.beam
	bootstrap/lib/stdlib/ebin/array.beam
	bootstrap/lib/stdlib/ebin/dets.beam
	bootstrap/lib/stdlib/ebin/edlin.beam
	bootstrap/lib/stdlib/ebin/erl_lint.beam
	bootstrap/lib/stdlib/ebin/ets.beam
	bootstrap/lib/stdlib/ebin/filelib.beam
	bootstrap/lib/stdlib/ebin/filename.beam
	bootstrap/lib/stdlib/ebin/gen_statem.beam
	bootstrap/lib/stdlib/ebin/lib.beam
	bootstrap/lib/stdlib/ebin/otp_internal.beam
	bootstrap/lib/stdlib/ebin/qlc.beam
	bootstrap/lib/stdlib/ebin/shell.beam
	bootstrap/lib/stdlib/ebin/stdlib.appup
	bootstrap/lib/stdlib/ebin/string.beam
	bootstrap/lib/stdlib/ebin/unicode_util.beam

* lukas/stdlib/maps_iterators/OTP-14012:
  erts: Limit size of first iterator for hashmaps
  Update primary bootstrap
  Update preloaded modules
  erts: Remove erts_internal:maps_to_list/2
  stdlib: Make io_lib and io_lib_pretty use maps iterator
  erts: Implement batching maps:iterator
  erts: Implement maps path iterator
  erts: Implement map iterator using a stack
  stdlib: Introduce maps iterator API

Conflicts:
	bootstrap/lib/stdlib/ebin/io_lib.beam
	bootstrap/lib/stdlib/ebin/io_lib_pretty.beam
	erts/emulator/beam/bif.tab
	erts/preloaded/ebin/erlang.beam
	erts/preloaded/ebin/erts_internal.beam
	erts/preloaded/ebin/zlib.beam