patch 8.1.2092: MS-Windows: redirect in system() does not work

Problem:    MS-Windows: redirect in system() does not work.
Solution:   Handle 'shellxescape' and 'shellxquote' better. (Yasuhiro
            Matsumoto, closes #2054)
diff --git a/src/misc2.c b/src/misc2.c
index f4da4c2..da274e6 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -3157,7 +3157,7 @@
 	{
 	    char_u *ecmd = cmd;
 
-	    if (*p_sxe != NUL && STRCMP(p_sxq, "(") == 0)
+	    if (*p_sxe != NUL && *p_sxq == '(')
 	    {
 		ecmd = vim_strsave_escaped_ext(cmd, p_sxe, '^', FALSE);
 		if (ecmd == NULL)
@@ -3168,11 +3168,11 @@
 	    {
 		STRCPY(ncmd, p_sxq);
 		STRCAT(ncmd, ecmd);
-		/* When 'shellxquote' is ( append ).
-		 * When 'shellxquote' is "( append )". */
-		STRCAT(ncmd, STRCMP(p_sxq, "(") == 0 ? (char_u *)")"
-			   : STRCMP(p_sxq, "\"(") == 0 ? (char_u *)")\""
-			   : p_sxq);
+		// When 'shellxquote' is ( append ).
+		// When 'shellxquote' is "( append )".
+		STRCAT(ncmd, *p_sxq == '(' ? (char_u *)")"
+		    : *p_sxq == '"' && *(p_sxq+1) == '(' ? (char_u *)")\""
+		    : p_sxq);
 		retval = mch_call_shell(ncmd, opt);
 		vim_free(ncmd);
 	    }