pg_upgrade: use pg_usleep(); remove Windows workaround

contrib/pg_upgrade/exec.c

@@ -102,7 +102,7 @@ static DWORD       mainThreadId = 0;
 
 		for (iter = 0; iter < 4 && log == NULL; iter++)
 		{
-			sleep(1);
+			pg_usleep(1000000);		/* 1 sec */
 			log = fopen(log_file, "a");
 		}
 	}

contrib/pg_upgrade/pg_upgrade.h

@@ -83,7 +83,6 @@ extern char *output_files[];
 #define pg_copy_file		CopyFile
 #define pg_mv_file			pgrename
 #define pg_link_file		win32_pghardlink
-#define sleep(x)			Sleep(x * 1000)
 #define PATH_SEPARATOR		'\\'
 #define RM_CMD				"DEL /q"
 #define RMDIR_CMD			"RMDIR /s/q"