Problem:    Spacing-combining characters handled as composing, causing text to
            take more space than expected.
Solution:   Handle characters marked with "Mc" not as composing.
            (closes vim/vim#11282
https://github.com/vim/vim/commit/7beaf6a720ddc7e2989c8831872bfb98ec78a65d

This was used in the past with assumption that curwin/curbuf
is "special" but this has not been true since basically forever
at this point.

Reduce NOT_VALID/CLEAR panic in options.lua . These should not
be set if an effect of the option is causing something
which by itself invokes redraw_later().

Problem:    Macros for MS-Windows are inconsistent, using "32", "3264 and
            others.
Solution:   Use MSWIN for all MS-Windows builds.  Use FEAT_GUI_MSWIN for the
            GUI build. (Hirohito Higashi, closes vim/vim#3932)
https://github.com/vim/vim/commit/4f97475d326c2773a78561fb874e4f23c25cbcd9

Work on https://github.com/neovim/neovim/issues/459

Co-authored-by: Famiu Haque <famiuhaque@protonmail.com>

Make the copy_object() family accept an optional arena. More than
half of the callsites should be refactored to use an arena later
anyway.

This is both simpler in client code and more effective (always reuse
block hottest in cache)

Problem:    It is not possible to specify cell widths of characters.
Solution:   Add setcellwidths().
https://github.com/vim/vim/commit/08aac3c6192f0103cb87e280270a32b50e653be1

Co-Authored-By: delphinus <me@delphinus.dev>

In case nvim A sends nvim_error_event to nvim B, it would
respond with another nvim_error_event due to unknown
request name. Fix this by adding dummy request handler for now.