Repair possible failure to update hint bits back to disk, per

http://archives.postgresql.org/pgsql-hackers/2004-10/msg00464.php.
This fix is intended to be permanent: it moves the responsibility for
calling SetBufferCommitInfoNeedsSave() into the tqual.c routines,
eliminating the requirement for callers to test whether t_infomask changed.
Also, tighten validity checking on buffer IDs in bufmgr.c --- several
routines were paranoid about out-of-range shared buffer numbers but not
about out-of-range local ones, which seems a tad pointless.

src/include/storage/bufmgr.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.86 2004/08/29 05:06:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.87 2004/10/15 22:40:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,13 +51,14 @@ extern int32 *LocalRefCount;
  * These routines are beaten on quite heavily, hence the macroization.
  */
 
-#define BAD_BUFFER_ID(bid) ((bid) < 1 || (bid) > NBuffers)
-
 /*
  * BufferIsValid
  *		True iff the given buffer number is valid (either as a shared
  *		or local buffer).
  *
+ * This is not quite the inverse of the BufferIsInvalid() macro, since this
+ * adds sanity rangechecks on the buffer number.
+ *
  * Note: For a long time this was defined the same as BufferIsPinned,
  * that is it would say False if you didn't hold a pin on the buffer.
  * I believe this was bogus and served only to mask logic errors.
@@ -66,10 +67,9 @@ extern int32 *LocalRefCount;
  */
 #define BufferIsValid(bufnum) \
 ( \
-	BufferIsLocal(bufnum) ? \
-		((bufnum) >= -NLocBuffer) \
-	: \
-		(! BAD_BUFFER_ID(bufnum)) \
+	(bufnum) != InvalidBuffer && \
+	(bufnum) >= -NLocBuffer && \
+	(bufnum) <= NBuffers \
 )
 
 /*
@@ -81,15 +81,13 @@ extern int32 *LocalRefCount;
  */
 #define BufferIsPinned(bufnum) \
 ( \
-	BufferIsLocal(bufnum) ? \
-		((bufnum) >= -NLocBuffer && LocalRefCount[-(bufnum) - 1] > 0) \
+	!BufferIsValid(bufnum) ? \
+		false \
 	: \
-	( \
-		BAD_BUFFER_ID(bufnum) ? \
-			false \
+		BufferIsLocal(bufnum) ? \
+			(LocalRefCount[-(bufnum) - 1] > 0) \
 		: \
 			(PrivateRefCount[(bufnum) - 1] > 0) \
-	) \
 )
 
 /*