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/runtime/doc/eval.txt b/runtime/doc/eval.txt
index b5bc100..bd92b3d 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -8077,6 +8077,9 @@
 		   "term_cols"	     horizontal size to use for the terminal,
 		   		     instead of using 'termsize'
 		   "vertical"	     split the window vertically
+		   "curwin"	     use the current window, do not split the
+				     window; fails if the current buffer
+				     cannot be |abandon|ed
 		   "term_finish"     What to do when the job is finished:
 					"close": close any windows
 					"open": open window if needed