Move log_newpage and log_newpage_buffer to xlog.c.

log_newpage is used by many indexams, in addition to heap, but for
historical reasons it's always been part of the heapam rmgr. Starting with
9.3, we have another WAL record type for logging an image of a page,
XLOG_FPI. Simplify things by moving log_newpage and log_newpage_buffer to
xlog.c, and switch to using the XLOG_FPI record type.

Bump the WAL version number because the code to replay the old HEAP_NEWPAGE
records is removed.

src/backend/access/transam/xlog.c

@@ -4084,7 +4084,14 @@ RestoreBackupBlockContents(XLogRecPtr lsn, BkpBlock bkpb, char *blk,
 	 * reset it here since it will be set before being written.
 	 */
 
-	PageSetLSN(page, lsn);
+	/*
+	 * The page may be uninitialized. If so, we can't set the LSN because that
+	 * would corrupt the page.
+	 */
+	if (!PageIsNew(page))
+	{
+		PageSetLSN(page, lsn);
+	}
 	MarkBufferDirty(buffer);
 
 	if (!keep_buffer)
@@ -8988,6 +8995,128 @@ XLogSaveBufferForHint(Buffer buffer, bool buffer_std)
 	return recptr;
 }
 
+/*
+ * Write a WAL record containing a full image of a page. Caller is responsible
+ * for writing the page to disk after calling this routine.
+ *
+ * Note: If you're using this function, you should be building pages in private
+ * memory and writing them directly to smgr.  If you're using buffers, call
+ * log_newpage_buffer instead.
+ *
+ * If the page follows the standard page layout, with a PageHeader and unused
+ * space between pd_lower and pd_upper, set 'page_std' to TRUE. That allows
+ * the unused space to be left out from the WAL record, making it smaller.
+ */
+XLogRecPtr
+log_newpage(RelFileNode *rnode, ForkNumber forkNum, BlockNumber blkno,
+			Page page, bool page_std)
+{
+	BkpBlock	bkpb;
+	XLogRecPtr	recptr;
+	XLogRecData rdata[3];
+
+	/* NO ELOG(ERROR) from here till newpage op is logged */
+	START_CRIT_SECTION();
+
+	bkpb.node = *rnode;
+	bkpb.fork = forkNum;
+	bkpb.block = blkno;
+
+	if (page_std)
+	{
+		/* Assume we can omit data between pd_lower and pd_upper */
+		uint16		lower = ((PageHeader) page)->pd_lower;
+		uint16		upper = ((PageHeader) page)->pd_upper;
+
+		if (lower >= SizeOfPageHeaderData &&
+			upper > lower &&
+			upper <= BLCKSZ)
+		{
+			bkpb.hole_offset = lower;
+			bkpb.hole_length = upper - lower;
+		}
+		else
+		{
+			/* No "hole" to compress out */
+			bkpb.hole_offset = 0;
+			bkpb.hole_length = 0;
+		}
+	}
+	else
+	{
+		/* Not a standard page header, don't try to eliminate "hole" */
+		bkpb.hole_offset = 0;
+		bkpb.hole_length = 0;
+	}
+
+	rdata[0].data = (char *) &bkpb;
+	rdata[0].len = sizeof(BkpBlock);
+	rdata[0].buffer = InvalidBuffer;
+	rdata[0].next = &(rdata[1]);
+
+	if (bkpb.hole_length == 0)
+	{
+		rdata[1].data = (char *) page;
+		rdata[1].len = BLCKSZ;
+		rdata[1].buffer = InvalidBuffer;
+		rdata[1].next = NULL;
+	}
+	else
+	{
+		/* must skip the hole */
+		rdata[1].data = (char *) page;
+		rdata[1].len = bkpb.hole_offset;
+		rdata[1].buffer = InvalidBuffer;
+		rdata[1].next = &rdata[2];
+
+		rdata[2].data = (char *) page + (bkpb.hole_offset + bkpb.hole_length);
+		rdata[2].len = BLCKSZ - (bkpb.hole_offset + bkpb.hole_length);
+		rdata[2].buffer = InvalidBuffer;
+		rdata[2].next = NULL;
+	}
+
+	recptr = XLogInsert(RM_XLOG_ID, XLOG_FPI, rdata);
+
+	/*
+	 * The page may be uninitialized. If so, we can't set the LSN because that
+	 * would corrupt the page.
+	 */
+	if (!PageIsNew(page))
+	{
+		PageSetLSN(page, recptr);
+	}
+
+	END_CRIT_SECTION();
+
+	return recptr;
+}
+
+/*
+ * Write a WAL record containing a full image of a page.
+ *
+ * Caller should initialize the buffer and mark it dirty before calling this
+ * function.  This function will set the page LSN.
+ *
+ * If the page follows the standard page layout, with a PageHeader and unused
+ * space between pd_lower and pd_upper, set 'page_std' to TRUE. That allows
+ * the unused space to be left out from the WAL record, making it smaller.
+ */
+XLogRecPtr
+log_newpage_buffer(Buffer buffer, bool page_std)
+{
+	Page		page = BufferGetPage(buffer);
+	RelFileNode rnode;
+	ForkNumber	forkNum;
+	BlockNumber blkno;
+
+	/* Shared buffers should be modified in a critical section. */
+	Assert(CritSectionCount > 0);
+
+	BufferGetTag(buffer, &rnode, &forkNum, &blkno);
+
+	return log_newpage(&rnode, forkNum, blkno, page, page_std);
+}
+
 /*
  * Check if any of the GUC parameters that are critical for hot standby
  * have changed, and update the value in pg_control file if necessary.