* lars/crypto/multiple-engine-load-21/OTP-15233:
  Updated the engine load functionality

* ingela/maint-21/inets/status-501/ERIERL-218/OTP-15215:
  inets: Prepare for release
  inets: Use status code 501 when no mod_* handles the request
  ssl: Make sure that a correct cipher suite is selected

* ingela/ssl/maint-21/ECC/ERIERL-210/OTP-15203:
  ssl: Prepare for release
  ssl: Make sure that a correct cipher suite is selected

- engine_load/3/4 can be called multiple times for same engine
  if it allows it (eg doesn't contain global data)
- ensure_engine_loaded/2/3 is new functions that guarantees that the engine
  is just loaded once by adding it to OpenSSL internal engine list and check that
  before loading.
- ensure_engine_unloaded/1/2 is new functions that is used to unload engines loaded with
  ensure_engine_loaded (remove it from OpenSSL internal engine list and then unload).
- new utility functions engine_by_id/1, engine_add/1, engine_remove/1,
  engine_get_id/1 and engine_get_name/1

Conflicts:
	lib/crypto/c_src/crypto.c

Conflicts:
	lib/inets/test/httpd_SUITE.erl