patch 8.0.0769: build problems with terminal on MS-Windows

Problem:    Build problems with terminal on MS-Windows using MSVC.
Solution:   Remove stdbool.h dependency. Only use ScreenLinesUC when it was
            allocated. Fix typos. (Ken Takata)
diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index 0f6a492..a7bf3b9 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -73,6 +73,7 @@
 else
 CHANNEL=$(GUI)
 endif
+# Set to yes to enable terminal support.
 TERMINAL=no