Exclude Git-specific .mailmap and the config files for the other CI
services for consistency with the already excluded ones for GitHub
Actions and AppVeyor CI.
This results in less clatter at the top level for the source archives.
Remove the Perl modules composing upmake from wxWidgets repository, it's too
difficult to maintain them both here and at https://github.com/vadz/upmake and
just keep the wxWidgets-specific upmake_script.pl here and generate
build/upmake_script itself from it using fatpack.
This also updates upmake to the latest 0.3 version, as a side effect.
Use slashes, not backslashes, in the paths.
Use "auto" for all text files under docs/msw as all of them could be opened in
Notepad.
Also use Unix EOLs for configure.in (and not just for configure).
