erlang: bump to version 17.4

Erlang/OTP 17.4 is a service release on the 17 track with mostly bug
fixes, but it does contain a number of new features and characteristics
improvements as well.

Some highlights of the release are:

  - eldap: Nearly all TCP options are possible to give in the
    eldap:open/2 call.
  - ssh: Added API functions ptty_alloc/3 and ptty_alloc/4, to allocate a
    pseudo tty.
  - ssl: Handle servers that may send an empty SNI extension to the client.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>