patch 8.0.0180: error E937 is used twice

Problem:    Error E937 is used both for duplicate key in JSON and for trying
            to delete a buffer that is in use.
Solution:   Rename the JSON error to E938. (Norio Takagi, closes #1376)
diff --git a/src/json.c b/src/json.c
index faaeab3..a9333cf 100644
--- a/src/json.c
+++ b/src/json.c
@@ -936,7 +936,7 @@
 			&& dict_find(top_item->jd_tv.vval.v_dict,
 						 top_item->jd_key, -1) != NULL)
 		{
-		    EMSG2(_("E937: Duplicate key in JSON: \"%s\""),
+		    EMSG2(_("E938: Duplicate key in JSON: \"%s\""),
 							     top_item->jd_key);
 		    clear_tv(&top_item->jd_key_tv);
 		    clear_tv(cur_item);
diff --git a/src/testdir/test_json.vim b/src/testdir/test_json.vim
index bd348fc..6616365 100644
--- a/src/testdir/test_json.vim
+++ b/src/testdir/test_json.vim
@@ -152,7 +152,7 @@
   call assert_fails('call json_decode("blah")', "E474:")
   call assert_fails('call json_decode("true blah")', "E488:")
   call assert_fails('call json_decode("<foobar>")', "E474:")
-  call assert_fails('call json_decode("{\"a\":1,\"a\":2}")', "E937:")
+  call assert_fails('call json_decode("{\"a\":1,\"a\":2}")', "E938:")
 
   call assert_fails('call json_decode("{")', "E474:")
   call assert_fails('call json_decode("{foobar}")', "E474:")
diff --git a/src/version.c b/src/version.c
index dd5f700..7b576af 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    180,
+/**/
     179,
 /**/
     178,