Cleanup more code and comments related to Windows NT4 (XP days)

All the code and comments cleaned up here is irrelevant since 495ed0e.
Note that this removes an assumption that CreateRestrictedToken() may
not exist, something that could have happened when running under Windows
NT as the code stated.  Rather than assuming that it may not exist, this
causes pg_ctl to fail hard if the function cannot be loaded.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20220826112637.GD2342@telsasoft.com

src/backend/port/win32/socket.c

@@ -495,7 +495,7 @@ pgwin32_send(SOCKET s, const void *buf, int len, int flags)
 			return -1;
 		}
 
-		/* No error, zero bytes (win2000+) or error+WSAEWOULDBLOCK (<=nt4) */
+		/* No error, zero bytes */
 
 		if (pgwin32_waitforsinglesocket(s, FD_WRITE | FD_CLOSE, INFINITE) == 0)
 			return -1;

src/bin/pg_ctl/pg_ctl.c

@@ -1726,9 +1726,7 @@ pgwin32_doRunAsService(void)
 
 /*
  * Mingw headers are incomplete, and so are the libraries. So we have to load
- * a whole lot of API functions dynamically. Since we have to do this anyway,
+ * a whole lot of API functions dynamically.
- * also load the couple of functions that *do* exist in mingw headers but not
- * on NT4. That way, we don't break on NT4.
  */
 typedef BOOL (WINAPI * __CreateRestrictedToken) (HANDLE, DWORD, DWORD, PSID_AND_ATTRIBUTES, DWORD, PLUID_AND_ATTRIBUTES, DWORD, PSID_AND_ATTRIBUTES, PHANDLE);
 typedef BOOL (WINAPI * __IsProcessInJob) (HANDLE, HANDLE, PBOOL);
@@ -1768,9 +1766,6 @@ InheritStdHandles(STARTUPINFO *si)
  *
  * Returns 0 on success, non-zero on failure, same as CreateProcess().
  *
- * On NT4, or any other system not containing the required functions, will
- * launch the process under the current token without doing any modifications.
- *
  * NOTE! Job object will only work when running as a service, because it's
  * automatically destroyed when pg_ctl exits.
  */
@@ -1815,14 +1810,10 @@ CreateRestrictedProcess(char *cmd, PROCESS_INFORMATION *processInfo, bool as_ser
 
 	if (_CreateRestrictedToken == NULL)
 	{
-		/*
+		/* Log error if we cannot get the function */
-		 * NT4 doesn't have CreateRestrictedToken, so just call ordinary
+		write_stderr(_("%s: could not locate object function to create restricted token: error code %lu\n"),
-		 * CreateProcess
+					 progname, (unsigned long) GetLastError());
-		 */
+		return 0;
-		write_stderr(_("%s: WARNING: cannot create restricted tokens on this platform\n"), progname);
-		if (Advapi32Handle != NULL)
-			FreeLibrary(Advapi32Handle);
-		return CreateProcess(NULL, cmd, NULL, NULL, FALSE, 0, NULL, NULL, &si, processInfo);
 	}
 
 	/* Open the current token to use as a base for the restricted one */

src/interfaces/libpq/win32.c

@@ -271,10 +271,6 @@ struct MessageDLL
  * Returns a description of the socket error by first trying
  * to find it in the lookup table, and if that fails, tries
  * to load any of the winsock dlls to find that message.
- * The DLL thing works from Nt4 (spX ?) up, but some special
- * versions of winsock might have this as well (seen on Win98 SE
- * special install)			   / Magnus Naeslund (mag@fbab.net)
- *
  */
 
 const char *

src/port/dirmod.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *	This includes replacement versions of functions that work on
- *	Win32 (NT4 and newer).
+ *	Windows.
  *
  * IDENTIFICATION
  *	  src/port/dirmod.c