Problem:
"set filetype=man" assumes the user wants :Man features, this does extra
stuff like renaming the buffer as "man://".
Solution:
- old entrypoint was ":set filetype=man", but this is too presumptuous #15487
- make the entrypoints more explicit:
1. when the ":Man" command is run
2. when a "man://" buffer is opened
- remove the tricky b:man_sect checks in ftplugin/man.vim and syntax/man.vim
- MANPAGER is supported via ":Man!", as documented.
fixes#15487
b6b12ea7c3
