Put all the prototypes for hashfn.c into the same header file.

Previously, some of the prototypes for functions in hashfn.c were
in utils/hashutils.h and others were in utils/hsearch.h, but that
is confusing and has no particular benefit.

Patch by me, reviewed by Suraj Kharage and Mark Dilger.

Discussion: http://postgr.es/m/CA+TgmoaRiG4TXND8QuM6JXFRkM_1wL2ZNhzaUKsuec9-4yrkgw@mail.gmail.com

src/backend/lib/dshash.c

@@ -35,7 +35,7 @@
 #include "storage/ipc.h"
 #include "storage/lwlock.h"
 #include "utils/dsa.h"
-#include "utils/hsearch.h"
+#include "utils/hashutils.h"
 #include "utils/memutils.h"
 
 /*

src/backend/utils/hash/dynahash.c

@@ -89,6 +89,7 @@
 #include "storage/shmem.h"
 #include "storage/spin.h"
 #include "utils/dynahash.h"
+#include "utils/hashutils.h"
 #include "utils/memutils.h"
 
 

src/include/utils/hashutils.h

@@ -26,6 +26,12 @@ extern Datum hash_any_extended(const unsigned char *k,
 extern Datum hash_uint32(uint32 k);
 extern Datum hash_uint32_extended(uint32 k, uint64 seed);
 
+extern uint32 string_hash(const void *key, Size keysize);
+extern uint32 tag_hash(const void *key, Size keysize);
+extern uint32 uint32_hash(const void *key, Size keysize);
+
+#define oid_hash uint32_hash	/* Remove me eventually */
+
 /*
  * Combine two 32-bit hash values, resulting in another hash value, with
  * decent bit mixing.

src/include/utils/hsearch.h

@@ -118,6 +118,10 @@ typedef struct
 
 /*
  * prototypes for functions in dynahash.c
+ *
+ * Note: It is deprecated for callers of hash_create to explicitly specify
+ * string_hash, tag_hash, uint32_hash, or oid_hash.  Just set HASH_BLOBS or
+ * not.  Use HASH_FUNCTION only when you want something other than those.
  */
 extern HTAB *hash_create(const char *tabname, long nelem,
 						 HASHCTL *info, int flags);
@@ -142,17 +146,4 @@ extern Size hash_get_shared_size(HASHCTL *info, int flags);
 extern void AtEOXact_HashTables(bool isCommit);
 extern void AtEOSubXact_HashTables(bool isCommit, int nestDepth);
 
-/*
- * prototypes for functions in hashfn.c
- *
- * Note: It is deprecated for callers of hash_create to explicitly specify
- * string_hash, tag_hash, uint32_hash, or oid_hash.  Just set HASH_BLOBS or
- * not.  Use HASH_FUNCTION only when you want something other than those.
- */
-extern uint32 string_hash(const void *key, Size keysize);
-extern uint32 tag_hash(const void *key, Size keysize);
-extern uint32 uint32_hash(const void *key, Size keysize);
-
-#define oid_hash uint32_hash	/* Remove me eventually */
-
 #endif							/* HSEARCH_H */