Streamline ephemeral key handling:

- drop support for ephemeral RSA keys (only allowed/needed
  for export ciphers)

- drop pTmpKeys from the per-process SSLModConfigRec, and remove
  the temp key generation at startup (unnecessary for DHE/ECDHE)

- unconditionally disable null and export-grade ciphers by always
  prepending "!aNULL:!eNULL:!EXP:" to any cipher suite string

- do not configure per-connection SSL_tmp_*_callbacks, as it is
  sufficient to set them for the SSL_CTX

- set default curve for ECDHE at startup, obviating the need
  for a per-handshake callback, for the time being (and also
  configure SSL_OP_SINGLE_ECDH_USE, previously left out)

For additional background, see
https://mail-archives.apache.org/mod_mbox/httpd-dev/201309.mbox/%3C52358ED1.2070704@velox.ch%3E


Follow-up fixes for r1526168:

- drop SSL_TMP_KEY_* constants from ssl_private.h, too

- make sure we also disable aNULL, eNULL and EXP ciphers
  for per-directory SSLCipherSuite directives

- apply the same treatment to SSLProxyCipherSuite


Increase minimum required OpenSSL version to 0.9.8a (in preparation
for the next mod_ssl commit, which will rely on the get_rfcX_prime_Y
functions added in that release):

- remove obsolete #defines / macros

- in ssl_private.h, regroup definitions based on whether
  they depend on TLS extension support or not

- for ECC and SRP support, set HAVE_X and change the rather awkward
  #ifndef OPENSSL_NO_X lines accordingly

For the discussion prior to taking this step, see
https://mail-archives.apache.org/mod_mbox/httpd-dev/201309.mbox/%3C524275C7.9060408%40velox.ch%3E


Improve ephemeral key handling (companion to r1526168):

- allow to configure custom DHE or ECDHE parameters via the
  SSLCertificateFile directive, and adapt its documentation
  accordingly (addresses PR 49559)

- add standardized DH parameters from RFCs 2409 and 3526,
  use them based on the length of the certificate's RSA/DSA key,
  and add a FAQ entry for clients which limit DH support
  to 1024 bits (such as Java 7 and earlier)

- move ssl_dh_GetParamFromFile() from ssl_engine_dh.c to
  ssl_util_ssl.c, and add ssl_ec_GetParamFromFile()

- drop ssl_engine_dh.c from mod_ssl

For the standardized DH parameters, OpenSSL version 0.9.8a
or later is required, which was therefore made a new minimum
requirement in r1527294.


PR 55616 (add missing APLOGNO), part 2
Submitted by: kbrand
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1542327 13f79535-47bb-0310-9956-ffa450edef68