[PATCH] configure-time knob to set default ssl ciphers

Hi hackers,

in Fedora, there's crypto initiative where people try to consolidate ssl
cipher settings for (majority of) Fedora services (PostgreSQL is
included).

PostgreSQL server uses 'HIGH:MEDIUM:+3DES:!aNULL' cipher set by default,
but what Fedora would like to have is 'PROFILE=SYSTEM' (works with
Fedora-patched OpenSSL, so please don't waste your time with checking this
elsewhere). What that really does is:

kEECDH:kRSA:kEDH:kPSK:kDHEPSK:kECDHEPSK:!EXP:!DES:!RC4:!RC2:!IDEA\
:!SEED:!eNULL:!aNULL:!MD5:!SSLv2

.. but that's just for the record (should be subset of upstream default);
more info in RH bug [1].

I'd like to propose the attached patch, so we could (without downstream
patching) do
$ ./configure ... --with-openssl-be-ciphers=PROFILE=SYSTEM

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1348125

Thanks for considering!
Pavel