patch 8.0.0731: cannot build the terminal feature on MS-Windows

Problem:    Cannot build the terminal feature on MS-Windows.
Solution:   Add the Makefile changes. (Yasuhiro Matsumoto, closes #1851)
diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index b292720..95619c4 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -73,6 +73,7 @@
 else
 CHANNEL=$(GUI)
 endif
+TERMINAL=no
 
 
 # Link against the shared version of libstdc++ by default.  Set
@@ -557,6 +558,10 @@
 DEFINES += -DFEAT_JOB_CHANNEL
 endif
 
+ifeq ($(TERMINAL),yes)
+DEFINES += -DFEAT_TERMINAL
+endif
+
 # DirectWrite (DirectX)
 ifeq ($(DIRECTX),yes)
 # Only allow DirectWrite for a GUI build.
@@ -743,6 +748,10 @@
 endif
 endif
 
+ifeq ($(TERMINAL),yes)
+OBJ += $(OUTDIR)/terminal.o
+endif
+
 
 ifdef MZSCHEME
 MZSCHEME_SUFFIX = Z