Session cache interface redesign, Part 6:

Move mutex handling up out of the session cache providers:

* modules/ssl/ssl_private.h (modssl_sesscache_provider): Add name and 
  flags fields.  Define MODSSL_SESSCACHE_FLAG_NOTMPSAFE constant.

* modules/ssl/ssl_scache.c (ssl_scache_store, ssl_scache_retrieve,
  ssl_scache_remove, ssl_ext_status_hook): Lock and release the mutex
  around provider calls, if necessary.

* modules/ssl/ssl_engine_mutex.c (ssl_mutex_init): Do nothing if no
  session cache is configured, or the session cache does not require a
  mutex.  Otherwise, fail if no mutex is configured and the session
  cache *does* require a mutex.
  (ssl_mutex_on, ssl_mutex_off): Remove checks for mutex mode;
  functions now invoked only if necessary.

* modules/ssl/ssl_scache_dc.c, modules/ssl/ssl_scache_memcache: Set
  name and flags fields in provider structures.

* modules/ssl/ssl_scache_shmcb.c, modules/ssl_scache_dbm.c: Remove
  mutex handling through; set name and flags fields in provider
  structures; mark both as unsafe for concurrent access in flags.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@631297 13f79535-47bb-0310-9956-ffa450edef68