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)
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.
