In log_newpage_range(), heed forkNum and page_std arguments.

The function assumed forkNum=MAIN_FORKNUM and page_std=true, ignoring
the actual arguments.  Existing callers passed exactly those values, so
there's no live bug.  Back-patch to v12, where the function first
appeared, because another fix needs this.

Discussion: https://postgr.es/m/20191118045434.GA1173436@rfd.leadboat.com

src/backend/access/transam/xloginsert.c

@@ -1043,8 +1043,13 @@ log_newpage_range(Relation rel, ForkNumber forkNum,
 				  BlockNumber startblk, BlockNumber endblk,
 				  bool page_std)
 {
+	int			flags;
 	BlockNumber blkno;
 
+	flags = REGBUF_FORCE_IMAGE;
+	if (page_std)
+		flags |= REGBUF_STANDARD;
+
 	/*
 	 * Iterate over all the pages in the range. They are collected into
 	 * batches of XLR_MAX_BLOCK_ID pages, and a single WAL-record is written
@@ -1066,7 +1071,8 @@ log_newpage_range(Relation rel, ForkNumber forkNum,
 		nbufs = 0;
 		while (nbufs < XLR_MAX_BLOCK_ID && blkno < endblk)
 		{
-			Buffer		buf = ReadBuffer(rel, blkno);
+			Buffer		buf = ReadBufferExtended(rel, forkNum, blkno,
+												 RBM_NORMAL, NULL);
 
 			LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
 
@@ -1088,7 +1094,7 @@ log_newpage_range(Relation rel, ForkNumber forkNum,
 		START_CRIT_SECTION();
 		for (i = 0; i < nbufs; i++)
 		{
-			XLogRegisterBuffer(i, bufpack[i], REGBUF_FORCE_IMAGE | REGBUF_STANDARD);
+			XLogRegisterBuffer(i, bufpack[i], flags);
 			MarkBufferDirty(bufpack[i]);
 		}