* sverker/erl_interface/ei_decode_fun-fix/OTP-15996:
  erl_interface: Fix bug in ei_decode_fun for very old encoding

Found by valgrind test runs.

If the environment is empty, don't access the free_vars pointer
and don't allocate a zero-size buffer. Better safe than sorry.

to support zero copy decoding
and bit offset arguments for future unaligned bit strings.

"export" is a reserved C++ keyword.

lib/erl_interface/include/ei.h:290:9:
error: expected ‘;’ after struct definition
         } export;
         ^
lib/erl_interface/include/ei.h:290:11:
error: expected unqualified-id before ‘export’
         } export;
           ^

same as ei_get_type()

to do word wise check/copy for pure ASCII
if ARCH allows it (x86 and amd64).