Problem:    Peeking and flushing output slows down execution.
Solution:   Do not update the mode message when global_busy is set.  Do not
            flush when only peeking for a character. (Ken Takata)
https://github.com/vim/vim/commit/cb574f415486adff645ce384979bfecf27f5be8c

Omit inchar() change: it breaks too many tests.

N/A patches for version.c:

vim-patch:8.2.5170: tiny issues

Problem:    Tiny issues.
Solution:   Tiny improvements.
https://github.com/vim/vim/commit/944cc9ceba8868acd238264d4a3894803c566b37

Problem:    This doesn't give the right result: eval(string(v:true)). (Nikolay
            Pavlov)
Solution:   Make the string "v:true" instead of "true".
https://github.com/vim/vim/commit/f48aa160fdd7b8caa7678e1a2139244dd2bdc547

Test ":unlet self-referencing node in a List graph #6070" feeds many characters into typeahead, so a timeout of only 100 milliseconds sometimes fails. Change that timeout to 1000 milliseconds.

Problem:    maparg() does not provide enough information for mapset().
Solution:   Add "lhsraw" and "lhsrawalt" items.  Drop "simplified"
https://github.com/vim/vim/commit/9c65253fe702ea010afec11aa971acd542c35de2

vim-patch:9.0.0127: unused variable

Problem:    Unused variable.
Solution:   Remove the variable. (closes vim/vim#10829)
https://github.com/vim/vim/commit/e95f22f63a1871b91e5508088e5ae4905ce28cd7

Problem:    No error when assigning bool to a string option with setwinvar().
Solution:   Give an error (closes vim/vim#10766)
https://github.com/vim/vim/commit/28f84e17b068daca2635692d279930dcb7a150d0

Problem:
Since 0b9664f5240be4d9e9d6882fcd398970fd3a9532 powershell filtered
:[range]! commands with args causes error:
"Start-Process: A positional parameter cannot be found that accepts argument ..."

Solution:
Pass args to Start-Process via `-ArgumentList`.
closes #19250

exepath and stdpath should respect shellslash and return path with
proper file separator.
Closes #13787