patch 8.0.0910: cannot create a terminal in the current window

Problem:    Cannot create a terminal in the current window.
Solution:   Add option "curwin" and ++curwin.
diff --git a/src/channel.c b/src/channel.c
index 58b0b0c..9476276 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -4455,6 +4455,13 @@
 		opt->jo_set |= JO2_VERTICAL;
 		opt->jo_vertical = get_tv_number(item);
 	    }
+	    else if (STRCMP(hi->hi_key, "curwin") == 0)
+	    {
+		if (!(supported2 & JO2_CURWIN))
+		    break;
+		opt->jo_set |= JO2_CURWIN;
+		opt->jo_curwin = get_tv_number(item);
+	    }
 #endif
 	    else if (STRCMP(hi->hi_key, "env") == 0)
 	    {