Split hash.h → hash_xlog.h

Since the hash AM is going to be revamped to have WAL, this is a good
opportunity to clean up the include file a little bit to avoid including
a lot of extra stuff in the future.

Author: Amit Kapila

src/include/access/hash_xlog.h

@@ -0,0 +1,25 @@
+/*-------------------------------------------------------------------------
+ *
+ * hash_xlog.h
+ *	  header file for Postgres hash AM implementation
+ *
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/hash_xlog.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef HASH_XLOG_H
+#define HASH_XLOG_H
+
+#include "access/hash.h"
+#include "access/xlogreader.h"
+
+
+extern void hash_redo(XLogReaderState *record);
+extern void hash_desc(StringInfo buf, XLogReaderState *record);
+extern const char *hash_identify(uint8 info);
+
+#endif   /* HASH_XLOG_H */