Fix incidental warnings from cpluspluscheck.

Remove use of "register" keyword in hashfn.c.  It's obsolescent
according to recent C++ compilers, and no modern C compiler pays
much attention to it either.

Also fix one cosmetic warning about signed vs unsigned comparison.

Discussion: https://postgr.es/m/20518.1559494394@sss.pgh.pa.us

src/backend/utils/hash/hashfn.c

@@ -145,9 +145,9 @@
  * well mixed than c, however.
  */
 Datum
-hash_any(register const unsigned char *k, register int keylen)
+hash_any(const unsigned char *k, int keylen)
 {
-	register uint32 a,
+	uint32		a,
 				b,
 				c,
 				len;
@@ -160,7 +160,7 @@ hash_any(register const unsigned char *k, register int keylen)
 	if (((uintptr_t) k & UINT32_ALIGN_MASK) == 0)
 	{
 		/* Code path for aligned source data */
-		register const uint32 *ka = (const uint32 *) k;
+		const uint32 *ka = (const uint32 *) k;
 
 		/* handle most of the key */
 		while (len >= 12)
@@ -371,10 +371,10 @@ hash_any(register const unsigned char *k, register int keylen)
  * Returns a uint64 value.  Otherwise similar to hash_any.
  */
 Datum
-hash_any_extended(register const unsigned char *k, register int keylen,
+hash_any_extended(const unsigned char *k, int keylen,
 				  uint64 seed)
 {
-	register uint32 a,
+	uint32		a,
 				b,
 				c,
 				len;
@@ -400,7 +400,7 @@ hash_any_extended(register const unsigned char *k, register int keylen,
 	if (((uintptr_t) k & UINT32_ALIGN_MASK) == 0)
 	{
 		/* Code path for aligned source data */
-		register const uint32 *ka = (const uint32 *) k;
+		const uint32 *ka = (const uint32 *) k;
 
 		/* handle most of the key */
 		while (len >= 12)
@@ -612,7 +612,7 @@ hash_any_extended(register const unsigned char *k, register int keylen,
 Datum
 hash_uint32(uint32 k)
 {
-	register uint32 a,
+	uint32		a,
 				b,
 				c;
 
@@ -633,7 +633,7 @@ hash_uint32(uint32 k)
 Datum
 hash_uint32_extended(uint32 k, uint64 seed)
 {
-	register uint32 a,
+	uint32		a,
 				b,
 				c;
 

src/include/utils/expandeddatum.h

@@ -126,7 +126,7 @@ struct ExpandedObjectHeader
  */
 #define EOH_HEADER_MAGIC (-1)
 #define VARATT_IS_EXPANDED_HEADER(PTR) \
-	(((varattrib_4b *) (PTR))->va_4byte.va_header == EOH_HEADER_MAGIC)
+	(((varattrib_4b *) (PTR))->va_4byte.va_header == (uint32) EOH_HEADER_MAGIC)
 
 /*
  * Generic support functions for expanded objects.

src/include/utils/hashutils.h

@@ -20,9 +20,9 @@
 	(((v) >> 31) & UINT64CONST(0x100000001)))
 
 
-extern Datum hash_any(register const unsigned char *k, register int keylen);
-extern Datum hash_any_extended(register const unsigned char *k,
-							   register int keylen, uint64 seed);
+extern Datum hash_any(const unsigned char *k, int keylen);
+extern Datum hash_any_extended(const unsigned char *k,
+							   int keylen, uint64 seed);
 extern Datum hash_uint32(uint32 k);
 extern Datum hash_uint32_extended(uint32 k, uint64 seed);