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/sp_cache.h

@@ -21,6 +21,8 @@
 #pragma interface			/* gcc class implementation */
 #endif
 
+#include "my_global.h"                          /* ulong */
+
 /*
   Stored procedures/functions cache. This is used as follows:
    * Each thread has its own cache.
@@ -30,6 +32,7 @@
 
 class sp_head;
 class sp_cache;
+class sp_name;
 
 /*
   Cache usage scenarios: