4c31fd0b9665 made the merging of match contexts stricter;
in fact, a little bit too strict.

Two match contexts with different number of slots would
be downgraded to the 'term' type. The correct way is to
keep the match context but set the number of slots to the
lowest number of slots of the two match contexts.

https://bugs.erlang.org/browse/ERL-490

beam_validator could fail issue a diagnostic when a register
that was supposed to be a match context was not guaranteed to
be a match context.

The bug was in merging of types. Merging of a match context with
another term would result in a match context. That is wrong. Merging
should produce a more general type, not a narrower type. Also, the
valid slots in two match contexts should be combined with 'band', not
'bor'.

* john/compiler/fail-labels-in-blocks-otp-18/ERIERL-48/OTP-14522:
  compiler: Fix live regs update on allocate in validator
  Take fail labels into account when determining liveness in block ops

Conflicts:
	lib/compiler/src/beam_utils.erl

The state without pruned registers was passed on to test_heap
causing the validator to belive registers that aren't live
actually are live.

The sys_core_fold pass would do an unsafe "optimization" when an
apply operation did not have a variable in the function position
as in the following example:

> cat test1.core
module 'test1' ['test1'/2]
    attributes []
'i'/1 =
  fun (_f) -> _f
'test1'/2 =
  fun (_f, _x) ->
    apply apply 'i'/1 (_f) (_x)
end
> erlc test1.core
no_file: Warning: invalid function call

Reported-by: Mikael Pettersson

All keys in an orddict must be unique. sys_core_fold:sub_sub_scope/1
broke that rule. It was probably harmless, but it is better to
avoid such rule violations.

* hasse/unicode_atoms/OTP-14285:
  compiler: Handle (bad) Unicode parse transform module names
  kernel: Improve handling of Unicode filenames
  stdlib: Handle Unicode atoms in ms_transform
  stdlib: Improve Unicode handling of the Erlang parser
  stdlib: Handle unknown compiler options with Unicode
  stdlib: Handle Unicode macro names
  stdlib: Correct Unicode handling in escript
  dialyzer: Improve handling of Unicode
  parsetools: Improve handling of Unicode atoms
  stdlib: Handle Unicode atoms when formatting stacktraces
  stdlib: Add more checks of module names to the linter
  stdlib: Handle Unicode atoms better in io_lib_format
  stdlib: Handle Unicode atoms in c.erl