WL#3771
  "Audit Plugin Interface"
  Implement new plug-in type - AUDIT
  New plug-in: audit_null
    simply increments counter for how many times it was called.

include/Makefile.am:
  wl3771
    add new headers to distribution
include/mysql/plugin.h:
  wl3771
    define new AUDIT plugin type
    Split out fulltext plugin type into its own header
include/mysql/plugin.h.pp:
  wl3771
    no real API change, just re-arranged some code
include/mysql/plugin_audit.h:
  wl3771
    pluggable audit interface
include/mysql/plugin_ftparser.h:
  wl3771
    Split out fulltext plugin type into its own header
libmysqld/CMakeLists.txt:
  wl3771
    add sql_audit.cc to build
libmysqld/Makefile.am:
  wl3771
    add sql_audit.cc to build
plugin/audit_null:
  wl3771
    an example plugin for testing pluggable audit interface
plugin/audit_null/Makefile.am:
  wl3771
    an example plugin for testing pluggable audit interface
plugin/audit_null/audit_null.c:
  wl3771
    an example plugin for testing pluggable audit interface
plugin/audit_null/plug.in:
  wl3771
    an example plugin for testing pluggable audit interface
sql/CMakeLists.txt:
  wl3771
    add sql_audit.cc to build
sql/Makefile.am:
  wl3771
    add sql_audit.cc to build
sql/event_queue.cc:
  wl3771
    release audit resources before waiting
sql/log.cc:
  wl3771
    add general audit call for log
sql/mysqld.cc:
  wl3771
    add audit initialize/finalize
    add general audit call for error
sql/sql_audit.cc:
  wl3771
    pluggable audit interface implementation
sql/sql_audit.h:
  wl3771
    pluggable audit interface implementation
sql/sql_class.cc:
  wl3771
    add thd audit init/deinit calls
sql/sql_class.h:
  wl3771
    add required data structures for audit to THD
sql/sql_connect.cc:
  wl3771
    release audit resources before waiting
sql/sql_insert.cc:
  wl3771
    release audit plugins before waiting
sql/sql_parse.cc:
  wl3771
    add general audit call for results
sql/sql_plugin.cc:
  wl3771
    add declarations for audit plugin type