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

include/violite.h

@@ -30,6 +30,10 @@
 extern "C" {
 #endif /* __cplusplus */
 
+#ifdef __cplusplus
+typedef struct st_vio Vio;
+#endif /* __cplusplus */
+
 enum enum_vio_type
 {
   VIO_CLOSED, VIO_TYPE_TCPIP, VIO_TYPE_SOCKET, VIO_TYPE_NAMEDPIPE,