Add buffer_std flag to MarkBufferDirtyHint().

MarkBufferDirtyHint() writes WAL, and should know if it's got a
standard buffer or not. Currently, the only callers where buffer_std
is false are related to the FSM.

In passing, rename XLOG_HINT to XLOG_FPI, which is more descriptive.

Back-patch to 9.3.

src/backend/access/hash/hash.c

@@ -287,7 +287,7 @@ hashgettuple(PG_FUNCTION_ARGS)
 			/*
 			 * Since this can be redone later if needed, mark as a hint.
 			 */
-			MarkBufferDirtyHint(buf);
+			MarkBufferDirtyHint(buf, true);
 		}
 
 		/*