Fix a windows build failure (next-mr-runtime).

sql/sql_cache.cc:
  Use my_hash_init() on Windows as well.
sql/sql_class.h:
  Use struct Query_cache_block (not class) for forward declaration,
  realing the code to match 6.0 alignment.

sql/sql_cache.cc

@@ -2114,7 +2114,7 @@ ulong Query_cache::init_cache()
     file system) and so should use case insensitive collation for
     comparison.
   */
-  VOID(hash_init(&tables,
+  VOID(my_hash_init(&tables,
                     lower_case_table_names ? &my_charset_bin :
                     files_charset_info,
                     def_table_hash_size, 0, 0,query_cache_table_get_key, 0, 0));

sql/sql_class.h

@@ -280,6 +280,27 @@ public:
   LEX_COLUMN (const String& x,const  uint& y ): column (x),rights (y) {}
 };
 
+/**
+  Query_cache_tls -- query cache thread local data.
+*/
+
+struct Query_cache_block;
+
+struct Query_cache_tls
+{
+  /*
+    'first_query_block' should be accessed only via query cache
+    functions and methods to maintain proper locking.
+  */
+  Query_cache_block *first_query_block;
+  void set_first_query_block(Query_cache_block *first_query_block_arg)
+  {
+    first_query_block= first_query_block_arg;
+  }
+
+  Query_cache_tls() :first_query_block(NULL) {}
+};
+
 /* SIGNAL / RESIGNAL / GET DIAGNOSTICS */
 
 /**
@@ -315,27 +336,6 @@ typedef enum enum_diag_condition_item_name
 */
 extern const LEX_STRING Diag_condition_item_names[];
 
-/**
-  Query_cache_tls -- query cache thread local data.
-*/
-
-class Query_cache_block;
-
-struct Query_cache_tls
-{
-  /*
-    'first_query_block' should be accessed only via query cache
-    functions and methods to maintain proper locking.
-  */
-  Query_cache_block *first_query_block;
-  void set_first_query_block(Query_cache_block *first_query_block_arg)
-  {
-    first_query_block= first_query_block_arg;
-  }
-
-  Query_cache_tls() :first_query_block(NULL) {}
-};
-
 #include "sql_lex.h"				/* Must be here */
 
 class Delayed_insert;