Session cache interface redesign, Part 3:

Move provider-private context out of SSLModConfigRec and into an
opaque context pointer.  Use real error propagation in the ->init
functions rather than ssl_die().

* modules/ssl/ssl_private.h (modssl_sesscache_provider): Take a
  context out-parameter from ->init, and return an apr_status_t.
  Add context pointer as first arg for the other function types.
  (SSLModConfigRec): Remove tSessionCacheData* fields; add
  sesscache_context field.

* modules/ssl/ssl_scache.c (ssl_scache_init): Move once-per-process
  invocation check back into here.  
  (ssl_scache_*): Adjust to use context pointer.

* modules/ssl/ssl_scache_shmcb.c, modules/ssl/ssl_scache_dc.c,
  modules/ssl/ssl_scache_dbm.c: Adjust all implementations to use
  opaque context pointer.

* modules/ssl/ssl_scache_memcache.c: Move memcache context into the
  context structure rather than using global state.

* modules/ssl/ssl_engine_config.c: Remove handling of
  pSessionCacheData* fields in SSLModConfigRec.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@630323 13f79535-47bb-0310-9956-ffa450edef68