patch 8.2.0574: ipv6 feature not shown in :version output

Problem:    Ipv6 feature not shown in :version output.
Solution:   Add ipv6 in :version output. (Ozaki Kiichi, closes #5924)

runtime/doc/eval.txt

@@ -1,4 +1,4 @@
-*eval.txt*	For Vim version 8.2.  Last change: 2020 Apr 08
+*eval.txt*	For Vim version 8.2.  Last change: 2020 Apr 13
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -10870,6 +10870,7 @@ iconv			Can use iconv() for conversion.
 insert_expand		Compiled with support for CTRL-X expansion commands in
 			Insert mode. (always true)
 job			Compiled with support for |channel| and |job|
+ipv6			Compiled with support for IPv6 networking in |channel|.
 jumplist		Compiled with |jumplist| support.
 keymap			Compiled with 'keymap' support.
 lambda			Compiled with |lambda| support.

src/version.c

@@ -296,6 +296,11 @@ static char *(features[]) =
 	"-iconv",
 #endif
 	"+insert_expand",
+#ifdef FEAT_IPV6
+	"+ipv6",
+#else
+	"-ipv6",
+#endif
 #ifdef FEAT_JOB_CHANNEL
 	"+job",
 #else
@@ -741,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    574,
 /**/
     573,
 /**/