patch 8.0.0693: no terminal emulator support

Problem:    No terminal emulator support.  Cannot properly run commands in the
            GUI.  Cannot run a job interactively with an ssh connection.
Solution:   Very early implementation of the :terminal command.  Includes
            libvterm converted to ANSI C.  Many parts still missing.
diff --git a/src/proto/terminal.pro b/src/proto/terminal.pro
new file mode 100644
index 0000000..96ebb7d
--- /dev/null
+++ b/src/proto/terminal.pro
@@ -0,0 +1,3 @@
+/* terminal.c */
+void ex_terminal(exarg_T *eap);
+/* vim: set ft=c : */