patch 8.0.0804: terminal window functions not yet implemented

Problem:    Terminal window functions not yet implemented.
Solution:   Implement several functions. Add a first test. (Yasuhiro
            Matsumoto, closes #1871)
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 1f8d307..4eb634c 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -197,6 +197,7 @@
 	    test_syntax.res \
 	    test_system.res \
 	    test_tcl.res \
+	    test_terminal.res \
 	    test_textobjects.res \
 	    test_undo.res \
 	    test_usercommands.res \