WL#5030: Split and remove mysql_priv.h

This patch:

- Moves all definitions from the mysql_priv.h file into
  header files for the component where the variable is
  defined
- Creates header files if the component lacks one
- Eliminates all include directives from mysql_priv.h
- Eliminates all circular include cycles
- Rename time.cc to sql_time.cc
- Rename mysql_priv.h to sql_priv.h

plugin/daemon_example/daemon_example.cc

@@ -13,13 +13,17 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */
 
-#include <mysql_priv.h>
+#include <sql_priv.h>
 #include <stdlib.h>
 #include <ctype.h>
 #include <mysql_version.h>
 #include <mysql/plugin.h>
 #include <my_global.h>
 #include <my_dir.h>
+#include "my_pthread.h"                         // pthread_handler_t
+#include "my_sys.h"                             // my_write, my_malloc
+#include "m_string.h"                           // strlen
+#include "sql_plugin.h"                         // st_plugin_int
 
 /*
   Disable __attribute__() on non-gcc compilers.