patch 8.1.0880: MS-Windows: inconsistent selection of winpty/conpty

Problem:    MS-Windows: inconsistent selection of winpty/conpty.
Solution:   Name option 'termwintype', use ++type argument and "term_pty" for
            term_start(). (Hirohito Higashi, closes #3915)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index c9e2b0b..4133420 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -8054,23 +8054,6 @@
 	Note that the "cterm" attributes are still used, not the "gui" ones.
 	NOTE: This option is reset when 'compatible' is set.
 
-						*'termmode'* *'tmod'*
-'termmode' 'tmod'	string  (default "")
-			local to window
-			{not in Vi, MS-Windows only}
-	Whether the window uses winpty or |ConPTY| as the virtual console.
-	When set before opening the terminal, it influences what pty is used.
-	When opening the terminal it will be set to the actually used pty.
-
-	Possible values are:
-	    ""		use ConPTY if possible, winpty otherwise
-	    "winpty"	use winpty, fail if not supported
-	    "conpty"	use |ConPTY|, fail if not supported
-
-	|ConPTY| support depends on the platform (Windows 10 October 2018
-	edition).  winpty support needs to be installed.  If neither is
-	supported then you cannot open a terminal window.
-
 						*'termwinscroll'* *'twsl'*
 'termwinscroll' 'twsl'	number	(default 10000)
 			local to buffer
@@ -8119,6 +8102,24 @@
 	the size of the terminal.  In that case the Vim window will be
 	adjusted to that size, if possible.
 
+						*'termwintype'* *'twt'*
+'termwintype' 'twt'	string  (default "")
+			global
+			{not in Vi}
+			{only available when compiled with the |terminal|
+			feature on MS-Windows}
+	Specify the virtual console (pty) used when opening the terminal
+	window.
+
+	Possible values are:
+	    ""		use ConPTY if possible, winpty otherwise
+	    "winpty"	use winpty, fail if not supported
+	    "conpty"	use |ConPTY|, fail if not supported
+
+	|ConPTY| support depends on the platform (Windows 10 October 2018
+	edition).  winpty support needs to be installed.  If neither is
+	supported then you cannot open a terminal window.
+
 						*'terse'* *'noterse'*
 'terse'			boolean	(default off)
 			global