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

sql/protocol.cc

@@ -24,7 +24,10 @@
 #pragma implementation				// gcc: Class implementation
 #endif
 
-#include "mysql_priv.h"
+#include "sql_priv.h"
+#include "unireg.h"                    // REQUIRED: for other includes
+#include "protocol.h"
+#include "sql_class.h"                          // THD
 #include <stdarg.h>
 
 static const unsigned int PACKET_BUFFER_EXTRA_ALLOC= 1024;