Add a non-string identifier to window_procs for use in runtime
identification of the current window port being used.
Use a macro WPID to add the identification at the top of the
various existing window_procs declarations. It expands to the
existing text string, as well as the newly added field wp_id
with a wp_ identifier.
For example, WPID(tty) expands to: "tty", wp_tty
The generated wp_tty must be present in the wp_ids enum at
the top of include/winprocs.h.
The WINDOWPORT(x) macro has been updated to expand to a simple
value comparison (port.wp_id == wp_x), instead of a
string comparison.
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