patch 8.2.3864: cannot disable requesting key codes from xterm

Problem:    Cannot disable requesting key codes from xterm.
Solution:   Add the 'xtermcodes' option, default on.
diff --git a/src/option.h b/src/option.h
index 49d869b..a82258e 100644
--- a/src/option.h
+++ b/src/option.h
@@ -485,6 +485,7 @@
 #ifdef FEAT_EVAL
 EXTERN char_u	*p_ccv;		// 'charconvert'
 #endif
+EXTERN int	p_cdh;		// 'cdhome'
 EXTERN char_u	*p_cino;	// 'cinoptions'
 #ifdef FEAT_CMDWIN
 EXTERN char_u	*p_cedit;	// 'cedit'
@@ -1094,7 +1095,7 @@
 EXTERN int	p_wa;		// 'writeany'
 EXTERN int	p_wb;		// 'writebackup'
 EXTERN long	p_wd;		// 'writedelay'
-EXTERN int	p_cdh;		// 'cdhome'
+EXTERN int	p_xtermcodes;	// 'xtermcodes'
 
 /*
  * "indir" values for buffer-local options.
diff --git a/src/optiondefs.h b/src/optiondefs.h
index c392442..cc4ad9e 100644
--- a/src/optiondefs.h
+++ b/src/optiondefs.h
@@ -2941,6 +2941,9 @@
     {"writedelay",  "wd",   P_NUM|P_VI_DEF,
 			    (char_u *)&p_wd, PV_NONE,
 			    {(char_u *)0L, (char_u *)0L} SCTX_INIT},
+    {"xtermcodes",  NULL,   P_BOOL|P_VI_DEF,
+			    (char_u *)&p_xtermcodes, PV_NONE,
+			    {(char_u *)TRUE, (char_u *)0L} SCTX_INIT},
 
 // terminal output codes
 #define p_term(sss, vvv)   {sss, NULL, P_STRING|P_VI_DEF|P_RALL|P_SECURE, \
diff --git a/src/term.c b/src/term.c
index f74b18a..e97ec2c 100644
--- a/src/term.c
+++ b/src/term.c
@@ -4694,7 +4694,7 @@
 
 	// If xterm version >= 141 try to get termcap codes.  For other
 	// terminals the request should be ignored.
-	if (version >= 141)
+	if (version >= 141 && p_xtermcodes)
 	{
 	    LOG_TR(("Enable checking for XT codes"));
 	    check_for_codes = TRUE;
@@ -6446,8 +6446,7 @@
 	    if (name[0] == 'C' && name[1] == 'o')
 	    {
 		// Color count is not a key code.
-		i = atoi((char *)str);
-		may_adjust_color_count(i);
+		may_adjust_color_count(atoi((char *)str));
 	    }
 	    else
 	    {
diff --git a/src/version.c b/src/version.c
index 586d2ec..bbb2157 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3864,
+/**/
     3863,
 /**/
     3862,