Create DH parameters from OpenSSL at module init, avoiding (very

Create DH parameters from OpenSSL at module init, avoiding (very
minor) race and leaks:

* modules/ssl/ssl_engine_init.c (make_dh_params): Moved/rejigged
  variant of make_get_dh() macro.
  (init_dh_params, free_dh_params): New functions.
  (modssl_get_dh_params): Split out from ssl_callback_TmpDH.
  (ssl_init_Module, ssl_init_ModuleKill): Use new init_/free_.

* modules/ssl/ssl_engine_kernel.c: Moved out DH parameter handling.
  (ssl_callback_TmpDH): Use modssl_get_dh_params.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1598107 13f79535-47bb-0310-9956-ffa450edef68