Use STDOUT/STDERR_FILENO in most of syslogger.

This fixes problems on windows when logging collector is used in a service,
failing with:
FATAL:  could not redirect stderr: Bad file descriptor

This is triggered by 76e38b37a5. The problem is that STDOUT/STDERR_FILENO
aren't defined on windows, which lead us to use _fileno(stdout) etc, but that
doesn't work if stdout/stderr are closed.

Author: Andres Freund <andres@anarazel.de>
Reported-By: Sandeep Thakkar <sandeep.thakkar@enterprisedb.com>
Message-Id: 20220520164558.ozb7lm6unakqzezi@alap3.anarazel.de (on pgsql-packagers)
Backpatch: 15-, where 76e38b37a5 came in

src/backend/postmaster/syslogger.c

@@ -205,12 +205,12 @@ SysLoggerMain(int argc, char *argv[])
 		 * if they fail then presumably the file descriptors are closed and
 		 * any writes will go into the bitbucket anyway.
 		 */
-		close(fileno(stdout));
-		close(fileno(stderr));
+		close(STDOUT_FILENO);
+		close(STDERR_FILENO);
 		if (fd != -1)
 		{
-			(void) dup2(fd, fileno(stdout));
-			(void) dup2(fd, fileno(stderr));
+			(void) dup2(fd, STDOUT_FILENO);
+			(void) dup2(fd, STDERR_FILENO);
 			close(fd);
 		}
 	}
@@ -222,7 +222,7 @@ SysLoggerMain(int argc, char *argv[])
 	 */
 #ifdef WIN32
 	else
-		_setmode(_fileno(stderr), _O_TEXT);
+		_setmode(STDERR_FILENO, _O_TEXT);
 #endif
 
 	/*
@@ -716,12 +716,12 @@ SysLogger_Start(void)
 
 #ifndef WIN32
 				fflush(stdout);
-				if (dup2(syslogPipe[1], fileno(stdout)) < 0)
+				if (dup2(syslogPipe[1], STDOUT_FILENO) < 0)
 					ereport(FATAL,
 							(errcode_for_file_access(),
 							 errmsg("could not redirect stdout: %m")));
 				fflush(stderr);
-				if (dup2(syslogPipe[1], fileno(stderr)) < 0)
+				if (dup2(syslogPipe[1], STDERR_FILENO) < 0)
 					ereport(FATAL,
 							(errcode_for_file_access(),
 							 errmsg("could not redirect stderr: %m")));
@@ -738,12 +738,12 @@ SysLogger_Start(void)
 				fflush(stderr);
 				fd = _open_osfhandle((intptr_t) syslogPipe[1],
 									 _O_APPEND | _O_BINARY);
-				if (dup2(fd, _fileno(stderr)) < 0)
+				if (dup2(fd, STDERR_FILENO) < 0)
 					ereport(FATAL,
 							(errcode_for_file_access(),
 							 errmsg("could not redirect stderr: %m")));
 				close(fd);
-				_setmode(_fileno(stderr), _O_BINARY);
+				_setmode(STDERR_FILENO, _O_BINARY);
 
 				/*
 				 * Now we are done with the write end of the pipe.