Rename walmethod fsync method to sync

Using the name fsync clashed with the #define we have on Windows that
redefines it to _commit. Naming it sync should remove that conflict.

Per all the Windows buildfarm members

src/bin/pg_basebackup/receivelog.c

@@ -132,7 +132,7 @@ open_walfile(StreamCtl *stream, XLogRecPtr startpoint)
 			}
 
 			/* fsync file in case of a previous crash */
-			if (!stream->walmethod->fsync(f))
+			if (!stream->walmethod->sync(f))
 			{
 				stream->walmethod->close(f, CLOSE_UNLINK);
 				return false;
@@ -768,7 +768,7 @@ HandleCopyStream(PGconn *conn, StreamCtl *stream,
 		 */
 		if (stream->synchronous && lastFlushPosition < blockpos && walfile != NULL)
 		{
-			if (stream->walmethod->fsync(walfile) != 0)
+			if (stream->walmethod->sync(walfile) != 0)
 			{
 				fprintf(stderr, _("%s: could not fsync file \"%s\": %s\n"),
 						progname, current_walfile_name, stream->walmethod->getlasterror());
@@ -1011,7 +1011,7 @@ ProcessKeepaliveMsg(PGconn *conn, StreamCtl *stream, char *copybuf, int len,
 			 * data has been successfully replicated or not, at the normal
 			 * shutdown of the server.
 			 */
-			if (stream->walmethod->fsync(walfile) != 0)
+			if (stream->walmethod->sync(walfile) != 0)
 			{
 				fprintf(stderr, _("%s: could not fsync file \"%s\": %s\n"),
 						progname, current_walfile_name, stream->walmethod->getlasterror());

src/bin/pg_basebackup/walmethods.c

@@ -219,7 +219,7 @@ dir_close(Walfile f, WalCloseMethod method)
 }
 
 static int
-dir_fsync(Walfile f)
+dir_sync(Walfile f)
 {
 	Assert(f != NULL);
 
@@ -287,7 +287,7 @@ CreateWalDirectoryMethod(const char *basedir, bool sync)
 	method->get_current_pos = dir_get_current_pos;
 	method->get_file_size = dir_get_file_size;
 	method->close = dir_close;
-	method->fsync = dir_fsync;
+	method->sync = dir_sync;
 	method->existsfile = dir_existsfile;
 	method->finish = dir_finish;
 	method->getlasterror = dir_getlasterror;
@@ -606,7 +606,7 @@ tar_get_current_pos(Walfile f)
 }
 
 static int
-tar_fsync(Walfile f)
+tar_sync(Walfile f)
 {
 	Assert(f != NULL);
 	tar_clear_error();
@@ -764,7 +764,7 @@ tar_close(Walfile f, WalCloseMethod method)
 		return -1;
 
 	/* Always fsync on close, so the padding gets fsynced */
-	tar_fsync(f);
+	tar_sync(f);
 
 	/* Clean up and done */
 	pg_free(tf->pathname);
@@ -872,7 +872,7 @@ CreateWalTarMethod(const char *tarbase, int compression, bool sync)
 	method->get_current_pos = tar_get_current_pos;
 	method->get_file_size = tar_get_file_size;
 	method->close = tar_close;
-	method->fsync = tar_fsync;
+	method->sync = tar_sync;
 	method->existsfile = tar_existsfile;
 	method->finish = tar_finish;
 	method->getlasterror = tar_getlasterror;

src/bin/pg_basebackup/walmethods.h

@@ -29,7 +29,7 @@ struct WalWriteMethod
 
 	ssize_t		(*write) (Walfile f, const void *buf, size_t count);
 	off_t		(*get_current_pos) (Walfile f);
-	int			(*fsync) (Walfile f);
+	int			(*sync) (Walfile f);
 	bool		(*finish) (void);
 	char	   *(*getlasterror) (void);
 };