* john/compiler/fix-bad-bitstring-type-opt/OTP-15872:
  beam_ssa_type: Fix incorrect bitstring unit determination

The following sequence would be wrongly optimized into a
i_get_tuple_element2 instruction, reading an element from the
wrong tuple:

    {get_tuple_element,{x,0},1,{x,0}}.
    {get_tuple_element,{x,0},2,{x,1}}.

The compiler would treat the "Unit" of bs_init instructions as
the unit of the result instead of the required unit of the input,
causing is_binary checks to be wrongly optimized away.

* bjorn/compiler/fix-beam_ssa_dead-patch/OTP-15845:
  Fix unsafe optimizations where guard tests could be removed

* bjorng_ghub/bjorn/compiler/fix-beam_ssa_dead-crash/ERL-956/OTP-15848:
  Eliminate crash in the beam_ssa_dead compiler pass

* bjorn/compiler/fix-unloadable-code-patch/ERL-955/OTP-15846:
  Fix loading of Core Erlang code for extracting a map element

* bjorn/compiler/fix-beam_except/ERL-954/OTP-15839:
  Fix compiler crash in beam_except

* bjorn/compiler/fix-unsafe-type-inference/OTP-15838:
  Fix unsafe negative type inference

# Conflicts:
#	lib/compiler/src/beam_ssa_type.erl