* egil/erts/fix-configure-to-check-in-libsct-for-sctp-funcs/ERL-262/OTP-13956:
  Configure enable libsctp dependency
  Revert "Check libsctp for sctp funcs in configure.in"

* bjorn/erts/erl_prim_loader/OTP-14009:
  Update preloaded modules
  Fix performance bug in erl_prim_loader:get_modules/{2,3}

* egil/19/erts/fix-crashdump-sigusr1/OTP-13997:
  erts: Fix SIGUSR1 crashdump generation

This reverts commit 52fae83743a6e84d719f4f82fe45e6e0efdbd6f0:

    Check libsctp for sctp funcs in configure.in

    Call AC_CHECK_LIB before calling AC_CHECK_FUNCS to check for functions in libsctp.
    Otherwise AC_CHECK_FUNCS will not link with libsctp to see if function exists.

Reverting to the old behaviour of not checking for libsctp before checking for
sctp functions.  Then it works on Linux by loading libsctp and looking up the
symbols i runtime, and it works on FreeBSD since there is no separate libsctp
to link against - the functions are part of the default system libraries.

The erl_prim_loader:get_modules/{2,3} functions were introduced in
cd283583f8. Unfortunately, while the functions worked correctly, there
was a bug in that many garbage maessages would be sent to the
erl_prim_loader process.  The number of extra messages depended on
both the length of the code path and of the number of modules that
were fetched.  The messages were ignored and ultimately discarded,
causing no harm except for a performance degradation and increase of
the heap size for the erl_prim_loader process.

The following functions were hit by the performance bug:

  code:atomic_load/1
  code:ensure_modules_loaded/1
  code:prepare_loading/1