patch 8.0.0742: terminal feature does not work on MS-Windows

Problem:    Terminal feature does not work on MS-Windows.
Solution:   Use libvterm and libwinpty on MS-Windows. (Yasuhiro Matsumoto)
diff --git a/src/INSTALLpc.txt b/src/INSTALLpc.txt
index 5661f96..562b42c 100644
--- a/src/INSTALLpc.txt
+++ b/src/INSTALLpc.txt
@@ -29,10 +29,11 @@
 10. Building with Perl support
 11. Building with Ruby support
 12. Building with Tcl support
-13. Windows 3.1
-14. MS-DOS
+13. Building with Terminal support
+14. Windows 3.1
+15. MS-DOS
 
-15. Installing after building from sources
+16. Installing after building from sources
 
 
 The currently preferred method is using the free Visual C++ Toolkit 2008
@@ -702,19 +703,35 @@
         TCL=C:\Tcl86 DYNAMIC_TCL=yes TCL_VER=86 TCL_VER_LONG=8.6
 
 
-13. Windows 3.1x
+13. Building with Terminal support
+==================================
+
+Vim with Terminal support can be built with MinGW or Cygwin.
+Terminal support require winpty which provide following two files.
+
+    winpty.dll
+    winpty-agent.dll
+
+You can download following page:
+
+    https://github.com/rprichard/winpty
+
+It don't need header files or libraries. Just put them on your PATH.
+
+
+14. Windows 3.1x
 ================
 
 The Windows 3.1x support was removed in patch 7.4.1364.
 
 
-14. MS-DOS
+15. MS-DOS
 ==========
 
 The MS-DOS support was removed in patch 7.4.1399.
 
 
-15. Installing after building from sources
+16. Installing after building from sources
 ==========================================
 
 [provided by Michael Soyka]